1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1985-1987, 1993-1995, 1997, 1999-2012
3 @c Free Software Foundation, Inc.
4 @c See file emacs.texi for copying conditions.
5 @node Maintaining, Abbrevs, Building, Top
6 @chapter Maintaining Large Programs
8 This chapter describes Emacs features for maintaining large
12 * Version Control:: Using version control systems.
13 * Change Log:: Maintaining a change history for your program.
14 * Tags:: Go directly to any function in your program in one
15 command. Tags remembers which file it is in.
16 * EDE:: An integrated development environment for Emacs.
18 * Emerge:: A convenient way of merging two versions of a program.
23 @section Version Control
24 @cindex version control
26 A @dfn{version control system} is a program that can record multiple
27 versions of a source file, storing information such as the creation
28 time of each version, who made it, and a description of what was
31 The Emacs version control interface is called @dfn{VC}. VC commands
32 work with several different version control systems; currently, it
33 supports GNU Arch, Bazaar, CVS, Git, Mercurial, Monotone, RCS,
34 SCCS/CSSC, and Subversion. Of these, the GNU project distributes CVS,
35 Arch, RCS, and Bazaar.
37 VC is enabled automatically whenever you visit a file governed by a
38 version control system. To disable VC entirely, set the customizable
39 variable @code{vc-handled-backends} to @code{nil}
41 (@pxref{Customizing VC,,,emacs-xtra, Specialized Emacs Features}).
44 (@pxref{Customizing VC}).
48 * Introduction to VC:: How version control works in general.
49 * VC Mode Line:: How the mode line shows version control status.
50 * Basic VC Editing:: How to edit a file under version control.
51 * Log Buffer:: Features available in log entry buffers.
52 * Registering:: Putting a file under version control.
53 * Old Revisions:: Examining and comparing old versions.
54 * VC Change Log:: Viewing the VC Change Log.
55 * VC Undo:: Canceling changes before or after committing.
56 * VC Directory Mode:: Listing files managed by version control.
57 * Branches:: Multiple lines of development.
59 * Miscellaneous VC:: Various other commands and features of VC.
60 * Customizing VC:: Variables that change VC's behavior.
64 @node Introduction to VC
65 @subsection Introduction to Version Control
67 VC allows you to use a version control system from within Emacs,
68 integrating the version control operations smoothly with editing. It
69 provides a uniform interface for common operations in many version
72 Some uncommon or intricate version control operations, such as
73 altering repository settings, are not supported in VC. You should
74 perform such tasks outside Emacs, e.g.@: via the command line.
76 This section provides a general overview of version control, and
77 describes the version control systems that VC supports. You can skip
78 this section if you are already familiar with the version control system
82 * Why Version Control?:: Understanding the problems it addresses.
83 * Version Control Systems:: Supported version control back-end systems.
84 * VCS Concepts:: Words and concepts related to version control.
85 * VCS Merging:: How file conflicts are handled.
86 * VCS Changesets:: How changes are grouped.
87 * VCS Repositories:: Where version control repositories are stored.
88 * Types of Log File:: The VCS log in contrast to the ChangeLog.
91 @node Why Version Control?
92 @subsubsection Understanding the problems it addresses
94 Version control systems provide you with three important
99 @dfn{Reversibility}: the ability to back up to a previous state if you
100 discover that some modification you did was a mistake or a bad idea.
103 @dfn{Concurrency}: the ability to have many people modifying the same
104 collection of files knowing that conflicting modifications can be
105 detected and resolved.
108 @dfn{History}: the ability to attach historical data to your data,
109 such as explanatory comments about the intention behind each change to
110 it. Even for a programmer working solo, change histories are an
111 important aid to memory; for a multi-person project, they are a
112 vitally important form of communication among developers.
115 @node Version Control Systems
116 @subsubsection Supported Version Control Systems
118 @cindex back end (version control)
119 VC currently works with many different version control systems,
120 which it refers to as @dfn{back ends}:
126 SCCS was the first version control system ever built, and was long ago
127 superseded by more advanced ones. VC compensates for certain features
128 missing in SCCS (e.g.@: tag names for releases) by implementing them
129 itself. Other VC features, such as multiple branches, are simply
130 unavailable. Since SCCS is non-free, we recommend avoiding it.
134 CSSC is a free replacement for SCCS. You should use CSSC only if, for
135 some reason, you cannot use a more recent and better-designed version
140 RCS is the free version control system around which VC was initially
141 built. It is relatively primitive: it cannot be used over the
142 network, and works at the level of individual files. Almost
143 everything you can do with RCS can be done through VC.
147 CVS is the free version control system that was, until recently (circa
148 2008), used by the majority of free software projects. Nowadays, it
149 is slowly being superseded by newer systems. CVS allows concurrent
150 multi-user development either locally or over the network. Unlike
151 newer systems, it lacks support for atomic commits and file
152 moving/renaming. VC supports all basic editing operations under CVS.
157 Subversion (svn) is a free version control system designed to be
158 similar to CVS but without its problems (e.g., it supports atomic
159 commits of filesets, and versioning of directories, symbolic links,
160 meta-data, renames, copies, and deletes).
165 GNU Arch is one of the earliest @dfn{decentralized} version control
166 systems (the other being Monotone). @xref{VCS Concepts}, for a
167 description of decentralized version control systems. It is no longer
168 under active development, and has been deprecated in favor of Bazaar.
172 Git is a decentralized version control system originally invented by
173 Linus Torvalds to support development of Linux (his kernel). VC
174 supports many common Git operations, but others, such as repository
175 syncing, must be done from the command line.
180 Mercurial (hg) is a decentralized version control system broadly
181 resembling Git. VC supports most Mercurial commands, with the
182 exception of repository sync operations.
187 Bazaar (bzr) is a decentralized version control system that supports
188 both repository-based and decentralized versioning. VC supports most
189 basic editing operations under Bazaar.
193 @subsubsection Concepts of Version Control
196 @cindex registered file
197 When a file is under version control, we say that it is
198 @dfn{registered} in the version control system. The system has a
199 @dfn{repository} which stores both the file's present state and its
200 change history---enough to reconstruct the current version or any
201 earlier version. The repository also contains other information, such
202 as @dfn{log entries} that describe the changes made to each file.
205 @cindex checking out files
206 The copy of a version-controlled file that you actually edit is
207 called the @dfn{work file}. You can change each work file as you
208 would an ordinary file. After you are done with a set of changes, you
209 may @dfn{commit} (or @dfn{check in}) the changes; this records the
210 changes in the repository, along with a descriptive log entry.
213 A directory tree of work files is called a @dfn{working tree}.
217 Each commit creates a new @dfn{revision} in the repository. The
218 version control system keeps track of all past revisions and the
219 changes that were made in each revision. Each revision is named by a
220 @dfn{revision ID}, whose format depends on the version control system;
221 in the simplest case, it is just an integer.
223 To go beyond these basic concepts, you will need to understand three
224 aspects in which version control systems differ. As explained in the
225 next three sections, they can be lock-based or merge-based; file-based
226 or changeset-based; and centralized or decentralized. VC handles all
227 these modes of operation, but it cannot hide the differences.
230 @subsubsection Merge-based vs lock-based Version Control
232 A version control system typically has some mechanism to coordinate
233 between users who want to change the same file. There are two ways to
234 do this: merging and locking.
236 @cindex merging-based version
237 In a version control system that uses merging, each user may modify
238 a work file at any time. The system lets you @dfn{merge} your work
239 file, which may contain changes that have not been committed, with the
240 latest changes that others have committed.
242 @cindex locking-based version
243 Older version control systems use a @dfn{locking} scheme instead.
244 Here, work files are normally read-only. To edit a file, you ask the
245 version control system to make it writable for you by @dfn{locking}
246 it; only one user can lock a given file at any given time. This
247 procedure is analogous to, but different from, the locking that Emacs
248 uses to detect simultaneous editing of ordinary files
249 (@pxref{Interlocking}). When you commit your changes, that unlocks
250 the file, and the work file becomes read-only again. Other users may
251 then lock the file to make their own changes.
253 Both locking and merging systems can have problems when multiple
254 users try to modify the same file at the same time. Locking systems
255 have @dfn{lock conflicts}; a user may try to check a file out and be
256 unable to because it is locked. In merging systems, @dfn{merge
257 conflicts} happen when you commit a change to a file that conflicts
258 with a change committed by someone else after your checkout. Both
259 kinds of conflict have to be resolved by human judgment and
260 communication. Experience has shown that merging is superior to
261 locking, both in convenience to developers and in minimizing the
262 number and severity of conflicts that actually occur.
264 SCCS always uses locking. RCS is lock-based by default but can be
265 told to operate in a merging style. CVS and Subversion are
266 merge-based by default but can be told to operate in a locking mode.
267 Decentralized version control systems, such as GNU Arch, Git, and
268 Mercurial, are exclusively merging-based.
270 VC mode supports both locking and merging version control. The
271 terms ``commit'' and ``update'' are used in newer version control
272 systems; older lock-based systems use the terms ``check in'' and
273 ``check out''. VC hides the differences between them as much as
277 @subsubsection Changeset-based vs File-based Version Control
279 @cindex file-based version control
280 On SCCS, RCS, CVS, and other early version control systems, version
281 control operations are @dfn{file-based}: each file has its own comment
282 and revision history separate from that of all other files. Newer
283 systems, beginning with Subversion, are @dfn{changeset-based}: a
284 commit may include changes to several files, and the entire set of
285 changes is handled as a unit. Any comment associated with the change
286 does not belong to a single file, but to the changeset itself.
288 @cindex changeset-based version control
289 Changeset-based version control is more flexible and powerful than
290 file-based version control; usually, when a change to multiple files
291 has to be reversed, it's good to be able to easily identify and remove
294 @node VCS Repositories
295 @subsubsection Decentralized vs Centralized Repositories
297 @cindex centralized version control
298 @cindex decentralized version control
299 @cindex distributed version control
300 Early version control systems were designed around a
301 @dfn{centralized} model in which each project has only one repository
302 used by all developers. SCCS, RCS, CVS, and Subversion share this
303 kind of model. One of its drawbacks is that the repository is a choke
304 point for reliability and efficiency.
306 GNU Arch pioneered the concept of @dfn{distributed} or
307 @dfn{decentralized} version control, later implemented in Git,
308 Mercurial, and Bazaar. A project may have several different
309 repositories, and these systems support a sort of super-merge between
310 repositories that tries to reconcile their change histories. In
311 effect, there is one repository for each developer, and repository
312 merges take the place of commit operations.
314 VC helps you manage the traffic between your personal workfiles and
315 a repository. Whether the repository is a single master, or one of a
316 network of peer repositories, is not something VC has to care about.
318 @node Types of Log File
319 @subsubsection Types of Log File
320 @cindex types of log file
321 @cindex log File, types of
322 @cindex version control log
324 Projects that use a version control system can have two types of log
325 for changes. One is the log maintained by the version control system:
326 each time you commit a change, you fill out a @dfn{log entry} for the
327 change (@pxref{Log Buffer}). This is called the @dfn{version control
330 The other kind of log is the file @file{ChangeLog} (@pxref{Change
331 Log}). It provides a chronological record of all changes to a large
332 portion of a program---typically one directory and its subdirectories.
333 A small program would use one @file{ChangeLog} file; a large program
334 may have a @file{ChangeLog} file in each major directory.
335 @xref{Change Log}. Programmers have used change logs since long
336 before version control systems.
338 Changeset-based version systems typically maintain a changeset-based
339 modification log for the entire system, which makes change log files
340 somewhat redundant. One advantage that they retain is that it is
341 sometimes useful to be able to view the transaction history of a
342 single directory separately from those of other directories.
344 A project maintained with version control can use just the version
345 control log, or it can use both kinds of logs. It can handle some
346 files one way and some files the other way. Each project has its
347 policy, which you should follow.
349 When the policy is to use both, you typically want to write an entry
350 for each change just once, then put it into both logs. You can write
351 the entry in @file{ChangeLog}, then copy it to the log buffer with
352 @kbd{C-c C-a} when committing the change (@pxref{Log Buffer}). Or you
353 can write the entry in the log buffer while committing the change, and
354 later use the @kbd{C-x v a} command to copy it to @file{ChangeLog}
356 (@pxref{Change Logs and VC,,,emacs-xtra, Specialized Emacs Features}).
359 (@pxref{Change Logs and VC}).
363 @subsection Version Control and the Mode Line
364 @cindex VC mode line indicator
366 When you visit a file that is under version control, Emacs indicates
367 this on the mode line. For example, @samp{Bzr-1223} says that Bazaar
368 is used for that file, and the current revision ID is 1223.
370 @cindex version control status
371 The character between the back-end name and the revision ID
372 indicates the @dfn{version control status} of the work file. In a
373 merge-based version control system, a @samp{-} character indicates
374 that the work file is unmodified, and @samp{:} indicates that it has
375 been modified. @samp{!} indicates that the file contains conflicts as
376 result of a recent merge operation (@pxref{Merging}), or that the file
377 was removed from the version control. Finally, @samp{?} means that
378 the file is under version control, but is missing from the working
381 In a lock-based system, @samp{-} indicates an unlocked file, and
382 @samp{:} a locked file; if the file is locked by another user (for
383 instance, @samp{jim}), that is displayed as @samp{RCS:jim:1.3}.
384 @samp{@@} means that the file was locally added, but not yet committed
385 to the master repository.
387 On a graphical display, you can move the mouse over this mode line
388 indicator to pop up a ``tool-tip'', which displays a more verbose
389 description of the version control status. Pressing @kbd{Mouse-1}
390 over the indicator pops up a menu of VC commands, identical to
391 @samp{Tools / Version Control} on the menu bar.
393 @vindex auto-revert-check-vc-info
394 When Auto Revert mode (@pxref{Reverting}) reverts a buffer that is
395 under version control, it updates the version control information in
396 the mode line. However, Auto Revert mode may not properly update this
397 information if the version control status changes without changes to
398 the work file, from outside the current Emacs session. If you set
399 @code{auto-revert-check-vc-info} to @code{t}, Auto Revert mode updates
400 the version control status information every
401 @code{auto-revert-interval} seconds, even if the work file itself is
402 unchanged. The resulting CPU usage depends on the version control
403 system, but is usually not excessive.
405 @node Basic VC Editing
406 @subsection Basic Editing under Version Control
410 Most VC commands operate on @dfn{VC filesets}. A VC fileset is a
411 collection of one or more files that a VC operation acts on. When you
412 type VC commands in a buffer visiting a version-controlled file, the
413 VC fileset is simply that one file. When you type them in a VC
414 Directory buffer, and some files in it are marked, the VC fileset
415 consists of the marked files (@pxref{VC Directory Mode}).
417 On modern changeset-based version control systems (@pxref{VCS
418 Changesets}), VC commands handle multi-file VC filesets as a group.
419 For example, committing a multi-file VC fileset generates a single
420 revision, containing the changes to all those files. On older
421 file-based version control systems like CVS, each file in a multi-file
422 VC fileset is handled individually; for example, a commit generates
423 one revision for each changed file.
427 Perform the next appropriate version control operation on the current
431 @findex vc-next-action
433 The principal VC command is a multi-purpose command, @kbd{C-x v v}
434 (@code{vc-next-action}), which performs the ``most appropriate''
435 action on the current VC fileset: either registering it with a version
436 control system, or committing it, or unlocking it, or merging changes
437 into it. The precise actions are described in detail in the following
438 subsections. You can use @kbd{C-x v v} either in a file-visiting
439 buffer or in a VC Directory buffer.
441 Note that VC filesets are distinct from the ``named filesets'' used
442 for viewing and visiting files in functional groups
443 (@pxref{Filesets}). Unlike named filesets, VC filesets are not named
444 and don't persist across sessions.
447 * VC With A Merging VCS:: Without locking: default mode for CVS.
448 * VC With A Locking VCS:: RCS in its default mode, SCCS, and optionally CVS.
449 * Advanced C-x v v:: Advanced features available with a prefix argument.
452 @node VC With A Merging VCS
453 @subsubsection Basic Version Control with Merging
455 On a merging-based version control system (i.e.@: most modern ones;
456 @pxref{VCS Merging}), @kbd{C-x v v} does the following:
460 If there is more than one file in the VC fileset and the files have
461 inconsistent version control statuses, signal an error. (Note,
462 however, that a fileset is allowed to include both ``newly-added''
463 files and ``modified'' files; @pxref{Registering}.)
466 If none of the files in the VC fileset are registered with a version
467 control system, register the VC fileset, i.e.@: place it under version
468 control. @xref{Registering}. If Emacs cannot find a system to
469 register under, it prompts for a repository type, creates a new
470 repository, and registers the VC fileset with it.
473 If every work file in the VC fileset is unchanged, do nothing.
476 If every work file in the VC fileset has been modified, commit the
477 changes. To do this, Emacs pops up a @samp{*vc-log*} buffer; type the
478 desired log entry for the new revision, followed by @kbd{C-c C-c} to
479 commit. @xref{Log Buffer}.
481 If committing to a shared repository, the commit may fail if the
482 repository that has been changed since your last update. In that
483 case, you must perform an update before trying again. On a
484 decentralized version control system, use @kbd{C-x v +} (@pxref{VC
485 Pull}) or @kbd{C-x v m} (@pxref{Merging}). On a centralized version
486 control system, type @kbd{C-x v v} again to merge in the repository
490 Finally, if you are using a centralized version control system, check
491 if each work file in the VC fileset is up-to-date. If any file has
492 been changed in the repository, offer to update it.
495 These rules also apply when you use RCS in its ``non-locking'' mode,
496 except that changes are not automatically merged from the repository.
497 Nothing informs you if another user has committed changes in the same
498 file since you began editing it; when you commit your revision, his
499 changes are removed (however, they remain in the repository and are
500 thus not irrevocably lost). Therefore, you must verify that the
501 current revision is unchanged before committing your changes. In
502 addition, locking is possible with RCS even in this mode: @kbd{C-x v
503 v} with an unmodified file locks the file, just as it does with RCS in
504 its normal locking mode (@pxref{VC With A Locking VCS}).
506 @node VC With A Locking VCS
507 @subsubsection Basic Version Control with Locking
509 On a locking-based version control system (such as SCCS, and RCS in
510 its default mode), @kbd{C-x v v} does the following:
514 If there is more than one file in the VC fileset and the files have
515 inconsistent version control statuses, signal an error.
518 If each file in the VC fileset is not registered with a version
519 control system, register the VC fileset. @xref{Registering}. If
520 Emacs cannot find a system to register under, it prompts for a
521 repository type, creates a new repository, and registers the VC
525 If each file is registered and unlocked, lock it and make it writable,
526 so that you can begin to edit it.
529 If each file is locked by you and contains changes, commit the
530 changes. To do this, Emacs pops up a @samp{*vc-log*} buffer; type the
531 desired log entry for the new revision, followed by @kbd{C-c C-c} to
532 commit (@pxref{Log Buffer}).
535 If each file is locked by you, but you have not changed it, release
536 the lock and make the file read-only again.
539 If each file is locked by another user, ask whether you want to
540 ``steal the lock''. If you say yes, the file becomes locked by you,
541 and a warning message is sent to the user who had formerly locked the
545 These rules also apply when you use CVS in locking mode, except
546 that CVS does not support stealing locks.
548 @node Advanced C-x v v
549 @subsubsection Advanced Control in @kbd{C-x v v}
551 @cindex revision ID in version control
552 When you give a prefix argument to @code{vc-next-action} (@kbd{C-u
553 C-x v v}), it still performs the next logical version control
554 operation, but accepts additional arguments to specify precisely how
559 @cindex specific version control system
560 You can specify the name of a version control system. This is useful
561 if the fileset can be managed by more than one version control system,
562 and Emacs fails to detect the correct one.
565 Otherwise, if using CVS or RCS, you can specify a revision ID.
567 If the fileset is modified (or locked), this makes Emacs commit with
568 that revision ID. You can create a new branch by supplying an
569 appropriate revision ID (@pxref{Branches}).
571 If the fileset is unmodified (and unlocked), this checks the specified
572 revision into the working tree. You can also specify a revision on
573 another branch by giving its revision or branch ID (@pxref{Switching
574 Branches}). An empty argument (i.e.@: @kbd{C-u C-x v v @key{RET}})
575 checks out the latest (``head'') revision on the current branch.
577 This signals an error on a decentralized version control system.
578 Those systems do not let you specify your own revision IDs, nor do
579 they use the concept of ``checking out'' individual files.
583 @subsection Features of the Log Entry Buffer
585 @cindex C-c C-c @r{(Log Edit mode)}
586 @findex log-edit-done
587 When you tell VC to commit a change, it pops up a buffer named
588 @samp{*vc-log*}. In this buffer, you should write a @dfn{log entry}
589 describing the changes you have made (@pxref{Why Version Control?}).
590 After you are done, type @kbd{C-c C-c} (@code{log-edit-done}) to exit
591 the buffer and commit the change, together with your log entry.
593 @cindex Log Edit mode
594 @cindex mode, Log Edit
595 @vindex vc-log-mode-hook
596 The major mode for the @samp{*vc-log*} buffer is Log Edit mode, a
597 variant of Text mode (@pxref{Text Mode}). On entering Log Edit mode,
598 Emacs runs the hooks @code{text-mode-hook} and @code{vc-log-mode-hook}
601 In the @samp{*vc-log*} buffer, you can write one or more @dfn{header
602 lines}, specifying additional information to be supplied to the
603 version control system. Each header line must occupy a single line at
604 the top of the buffer; the first line that is not a header line is
605 treated as the start of the log entry. For example, the following
606 header line states that the present change was not written by you, but
607 by another developer:
610 Author: J. R. Hacker <jrh@@example.com>
614 Apart from the @samp{Author} header, Emacs recognizes the headers
615 @samp{Date} (a manually-specified commit time) and @samp{Fixes} (a
616 reference to a bug fixed by the change). Not all version control
617 systems recognize all headers: Bazaar recognizes all three headers,
618 while Git, Mercurial, and Monotone recognize only @samp{Author} and
619 @samp{Date}. If you specify a header for a system that does not
620 support it, the header is treated as part of the log entry.
622 @kindex C-c C-f @r{(Log Edit mode)}
623 @findex log-edit-show-files
624 @kindex C-c C-d @r{(Log Edit mode)}
625 @findex log-edit-show-diff
626 While in the @samp{*vc-log*} buffer, the ``current VC fileset'' is
627 considered to be the fileset that will be committed if you type
628 @w{@kbd{C-c C-c}}. To view a list of the files in the VC fileset,
629 type @w{@kbd{C-c C-f}} (@code{log-edit-show-files}). To view a diff
630 of changes between the VC fileset and the version from which you
631 started editing (@pxref{Old Revisions}), type @kbd{C-c C-d}
632 (@code{log-edit-show-diff}).
634 @kindex C-c C-a @r{(Log Edit mode)}
635 @findex log-edit-insert-changelog
636 If the VC fileset includes one or more @file{ChangeLog} files
637 (@pxref{Change Log}), type @kbd{C-c C-a}
638 (@code{log-edit-insert-changelog}) to pull the relevant entries into
639 the @samp{*vc-log*} buffer. If the topmost item in each
640 @file{ChangeLog} was made under your user name on the current date,
641 this command searches that item for entries matching the file(s) to be
642 committed, and inserts them.
644 If you are using CVS or RCS, see @ref{Change Logs and VC}, for the
645 opposite way of working---generating ChangeLog entries from the Log
649 To abort a commit, just @strong{don't} type @kbd{C-c C-c} in that
650 buffer. You can switch buffers and do other editing. As long as you
651 don't try to make another commit, the entry you were editing remains
652 in the @samp{*vc-log*} buffer, and you can go back to that buffer at
653 any time to complete the commit.
655 @kindex M-n @r{(Log Edit mode)}
656 @kindex M-p @r{(Log Edit mode)}
657 @kindex M-s @r{(Log Edit mode)}
658 @kindex M-r @r{(Log Edit mode)}
659 You can also browse the history of previous log entries to duplicate
660 a commit comment. This can be useful when you want to make several
661 commits with similar comments. The commands @kbd{M-n}, @kbd{M-p},
662 @kbd{M-s} and @kbd{M-r} for doing this work just like the minibuffer
663 history commands (@pxref{Minibuffer History}), except that they are
664 used outside the minibuffer.
667 @subsection Registering a File for Version Control
671 Register the visited file for version control.
676 The command @kbd{C-x v i} (@code{vc-register}) @dfn{registers} each
677 file in the current VC fileset, placing it under version control.
678 This is essentially equivalent to the action of @kbd{C-x v v} on an
679 unregistered VC fileset (@pxref{Basic VC Editing}), except that if the
680 VC fileset is already registered, @kbd{C-x v i} signals an error
681 whereas @kbd{C-x v v} performs some other action.
683 To register a file, Emacs must choose a version control system. For
684 a multi-file VC fileset, the VC Directory buffer specifies the system
685 to use (@pxref{VC Directory Mode}). For a single-file VC fileset, if
686 the file's directory already contains files registered in a version
687 control system, or if the directory is part of a directory tree
688 controlled by a version control system, Emacs chooses that system. In
689 the event that more than one version control system is applicable,
690 Emacs uses the one that appears first in the variable
692 @code{vc-handled-backends}.
695 @code{vc-handled-backends} (@pxref{Customizing VC}).
697 If Emacs cannot find a version control system to register the file
698 under, it prompts for a repository type, creates a new repository, and
699 registers the file into that repository.
701 On most version control systems, registering a file with @kbd{C-x v
702 i} or @kbd{C-x v v} adds it to the ``working tree'' but not to the
703 repository. Such files are labeled as @samp{added} in the VC
704 Directory buffer, and show a revision ID of @samp{@@@@} in the mode
705 line. To make the registration take effect in the repository, you
706 must perform a commit (@pxref{Basic VC Editing}). Note that a single
707 commit can include both file additions and edits to existing files.
709 On a locking-based version control system (@pxref{VCS Merging}),
710 registering a file leaves it unlocked and read-only. Type @kbd{C-x v
711 v} if you wish to start editing it.
714 @subsection Examining And Comparing Old Revisions
718 Compare the work files in the current VC fileset with the versions you
719 started from (@code{vc-diff}). With a prefix argument, prompt for two
720 revisions of the current VC fileset and compare them. You can also
721 call this command from a Dired buffer (@pxref{Dired}).
725 Like @kbd{C-x v =}, but using Ediff. @xref{Top, Ediff, ediff, The
730 Compare the entire working tree to the revision you started from
731 (@code{vc-root-diff}). With a prefix argument, prompt for two
732 revisions and compare their trees.
735 Prompt for a revision of the current file, and visit it in a separate
736 buffer (@code{vc-revision-other-window}).
739 Display an annotated version of the current file: for each line, show
740 the latest revision in which it was modified (@code{vc-annotate}).
745 @kbd{C-x v =} (@code{vc-diff}) displays a @dfn{diff} which compares
746 each work file in the current VC fileset to the version(s) from which
747 you started editing. The diff is displayed in another window, in a
748 Diff mode buffer (@pxref{Diff Mode}) named @file{*vc-diff*}. The
749 usual Diff mode commands are available in this buffer. In particular,
750 the @kbd{g} (@code{revert-buffer}) command performs the file
751 comparison again, generating a new diff.
754 To compare two arbitrary revisions of the current VC fileset, call
755 @code{vc-diff} with a prefix argument: @kbd{C-u C-x v =}. This
756 prompts for two revision IDs (@pxref{VCS Concepts}), and displays a
757 diff between those versions of the fileset. This will not work
758 reliably for multi-file VC filesets, if the version control system is
759 file-based rather than changeset-based (e.g.@: CVS), since then
760 revision IDs for different files would not be related in any
763 Instead of the revision ID, some version control systems let you
764 specify revisions in other formats. For instance, under Bazaar you
765 can enter @samp{date:yesterday} for the argument to @kbd{C-u C-x v =}
766 (and related commands) to specify the first revision committed after
767 yesterday. See the documentation of the version control system for
770 If you invoke @kbd{C-x v =} or @kbd{C-u C-x v =} from a Dired buffer
771 (@pxref{Dired}), the file listed on the current line is treated as the
776 @kbd{M-x vc-ediff} works like @kbd{C-x v =}, except that it uses an
777 Ediff session. @xref{Top, Ediff, ediff, The Ediff Manual}.
782 @kbd{C-x v D} (@code{vc-root-diff}) is similar to @kbd{C-x v =}, but
783 it displays the changes in the entire current working tree (i.e.@: the
784 working tree containing the current VC fileset). If you invoke this
785 command from a Dired buffer, it applies to the working tree containing
788 @vindex vc-diff-switches
789 You can customize the @command{diff} options that @kbd{C-x v =} and
790 @kbd{C-x v D} use for generating diffs. The options used are taken
791 from the first non-@code{nil} value amongst the variables
792 @code{vc-@var{backend}-diff-switches}, @code{vc-diff-switches}, and
793 @code{diff-switches} (@pxref{Comparing Files}), in that order. Here,
794 @var{backend} stands for the relevant version control system,
795 e.g.@: @code{bzr} for Bazaar. Since @code{nil} means to check the
796 next variable in the sequence, either of the first two may use the
797 value @code{t} to mean no switches at all. Most of the
798 @code{vc-@var{backend}-diff-switches} variables default to @code{nil},
799 but some default to @code{t}; these are for version control systems
800 whose @code{diff} implementations do not accept common diff options,
803 @findex vc-revision-other-window
805 To directly examine an older version of a file, visit the work file
806 and type @kbd{C-x v ~ @var{revision} @key{RET}}
807 (@code{vc-revision-other-window}). This retrieves the file version
808 corresponding to @var{revision}, saves it to
809 @file{@var{filename}.~@var{revision}~}, and visits it in a separate
814 Many version control systems allow you to view files @dfn{annotated}
815 with per-line revision information, by typing @kbd{C-x v g}
816 (@code{vc-annotate}). This creates a new buffer (the ``annotate
817 buffer'') displaying the file's text, with each line colored to show
818 how old it is. Red text is new, blue is old, and intermediate colors
819 indicate intermediate ages. By default, the color is scaled over the
820 full range of ages, such that the oldest changes are blue, and the
821 newest changes are red.
823 When you give a prefix argument to this command, Emacs reads two
824 arguments using the minibuffer: the revision to display and annotate
825 (instead of the current file contents), and the time span in days the
826 color range should cover.
828 From the annotate buffer, these and other color scaling options are
829 available from the @samp{VC-Annotate} menu. In this buffer, you can
830 also use the following keys to browse the annotations of past revisions,
831 view diffs, or view log entries:
835 Annotate the previous revision, i.e.@: the revision before the one
836 currently annotated. A numeric prefix argument is a repeat count, so
837 @kbd{C-u 10 p} would take you back 10 revisions.
840 Annotate the next revision, i.e.@: the revision after the one
841 currently annotated. A numeric prefix argument is a repeat count.
844 Annotate the revision indicated by the current line.
847 Annotate the revision before the one indicated by the current line.
848 This is useful to see the state the file was in before the change on
849 the current line was made.
852 Show in a buffer the file revision indicated by the current line.
855 Display the diff between the current line's revision and the previous
856 revision. This is useful to see what the current line's revision
857 actually changed in the file.
860 Display the diff between the current line's revision and the previous
861 revision for all files in the changeset (for VC systems that support
862 changesets). This is useful to see what the current line's revision
863 actually changed in the tree.
866 Show the log of the current line's revision. This is useful to see
867 the author's description of the changes in the revision on the current
871 Annotate the working revision--the one you are editing. If you used
872 @kbd{p} and @kbd{n} to browse to other revisions, use this key to
873 return to your working revision.
876 Toggle the annotation visibility. This is useful for looking just at
877 the file contents without distraction from the annotations.
881 @subsection VC Change Log
885 Display the change history for the current fileset
886 (@code{vc-print-log}).
889 Display the change history for the current repository
890 (@code{vc-print-root-log}).
893 Display the changes that will be received with a pull operation
894 (@code{vc-log-incoming}).
897 Display the changes that will be sent by the next push operation
898 (@code{vc-log-outgoing}).
903 The command @kbd{C-x v l} (@code{vc-print-log}) displays a buffer
904 named @samp{*vc-change-log*}, showing the history of changes made to
905 the current file, including who made the changes, the dates, and the
906 log entry for each change (these are the same log entries you would
907 enter via the @samp{*vc-log*} buffer; @pxref{Log Buffer}). Point is
908 centered at the revision of the file currently being visited. With a
909 prefix argument, the command prompts for the revision to center on,
910 and the maximum number of revisions to display.
912 If you call @kbd{C-x v l} from a VC Directory buffer (@pxref{VC
913 Directory Mode}) or a Dired buffer (@pxref{Dired}), it applies to the
914 file listed on the current line.
916 @findex vc-print-root-log
917 @findex log-view-toggle-entry-display
918 @kbd{C-x v L} (@code{vc-print-root-log}) displays a
919 @samp{*vc-change-log*} buffer showing the history of the entire
920 version-controlled directory tree (RCS, SCCS, and CVS do not support
921 this feature). With a prefix argument, the command prompts for the
922 maximum number of revisions to display.
924 The @kbd{C-x v L} history is shown in a compact form, usually
925 showing only the first line of each log entry. However, you can type
926 @key{RET} (@code{log-view-toggle-entry-display}) in the
927 @samp{*vc-change-log*} buffer to reveal the entire log entry for the
928 revision at point. A second @key{RET} hides it again.
930 On a decentralized version control system, the @kbd{C-x v I}
931 (@code{vc-log-incoming}) command displays a log buffer showing the
932 changes that will be applied, the next time you run the version
933 control system's ``pull'' command to get new revisions from another
934 repository (@pxref{VC Pull}). This other repository is the default
935 one from which changes are pulled, as defined by the version control
936 system; with a prefix argument, @code{vc-log-incoming} prompts for a
937 specific repository. Similarly, @kbd{C-x v O}
938 (@code{vc-log-outgoing}) shows the changes that will be sent to
939 another repository, the next time you run the ``push'' command; with a
940 prefix argument, it prompts for a specific destination repository.
942 In the @samp{*vc-change-log*} buffer, you can use the following keys
943 to move between the logs of revisions and of files, and to examine and
944 compare past revisions (@pxref{Old Revisions}):
948 Move to the previous revision entry. (Revision entries in the log
949 buffer are usually in reverse-chronological order, so the previous
950 revision-item usually corresponds to a newer revision.) A numeric
951 prefix argument is a repeat count.
954 Move to the next revision entry. A numeric prefix argument is a
958 Move to the log of the previous file, if showing logs for a multi-file
959 VC fileset. Otherwise, just move to the beginning of the log. A
960 numeric prefix argument is a repeat count.
963 Move to the log of the next file, if showing logs for a multi-file VC
964 fileset. A numeric prefix argument is a repeat count.
967 Annotate the revision on the current line (@pxref{Old Revisions}).
970 Modify the change comment displayed at point. Note that not all VC
971 systems support modifying change comments.
974 Visit the revision indicated at the current line.
977 Display a diff between the revision at point and the next earlier
978 revision, for the specific file.
981 Display the changeset diff between the revision at point and the next
982 earlier revision. This shows the changes to all files made in that
986 In a compact-style log buffer (e.g.@: the one created by @kbd{C-x v
987 L}), toggle between showing and hiding the full log entry for the
991 @vindex vc-log-show-limit
992 Because fetching many log entries can be slow, the
993 @samp{*vc-change-log*} buffer displays no more than 2000 revisions by
994 default. The variable @code{vc-log-show-limit} specifies this limit;
995 if you set the value to zero, that removes the limit. You can also
996 increase the number of revisions shown in an existing
997 @samp{*vc-change-log*} buffer by clicking on the @samp{Show 2X
998 entries} or @samp{Show unlimited entries} buttons at the end of the
999 buffer. However, RCS, SCCS, and CVS do not support this feature.
1002 @subsection Undoing Version Control Actions
1006 Revert the work file(s) in the current VC fileset to the last revision
1010 @c `C-x v c' (vc-rollback) was removed, since it's RCS/SCCS specific.
1014 @vindex vc-revert-show-diff
1015 If you want to discard all the changes you have made to the current
1016 VC fileset, type @kbd{C-x v u} (@code{vc-revert-buffer}). This shows
1017 you a diff between the work file(s) and the revision from which you
1018 started editing, and asks for confirmation for discarding the changes.
1019 If you agree, the fileset is reverted. If you don't want @kbd{C-x v
1020 u} to show a diff, set the variable @code{vc-revert-show-diff} to
1021 @code{nil} (you can still view the diff directly with @kbd{C-x v =};
1022 @pxref{Old Revisions}). Note that @kbd{C-x v u} cannot be reversed
1023 with the usual undo commands (@pxref{Undo}), so use it with care.
1025 On locking-based version control systems, @kbd{C-x v u} leaves files
1026 unlocked; you must lock again to resume editing. You can also use
1027 @kbd{C-x v u} to unlock a file if you lock it and then decide not to
1030 @node VC Directory Mode
1031 @subsection VC Directory Mode
1033 @cindex VC Directory buffer
1034 The @dfn{VC Directory buffer} is a specialized buffer for viewing
1035 the version control statuses of the files in a directory tree, and
1036 performing version control operations on those files. In particular,
1037 it is used to specify multi-file VC filesets for commands like
1038 @w{@kbd{C-x v v}} to act on (@pxref{VC Directory Commands}).
1042 To use the VC Directory buffer, type @kbd{C-x v d} (@code{vc-dir}).
1043 This reads a directory name using the minibuffer, and switches to a VC
1044 Directory buffer for that directory. By default, the buffer is named
1045 @samp{*vc-dir*}. Its contents are described
1050 in @ref{VC Directory Buffer}.
1053 The @code{vc-dir} command automatically detects the version control
1054 system to be used in the specified directory. In the event that more
1055 than one system is being used in the directory, you should invoke the
1056 command with a prefix argument, @kbd{C-u C-x v d}; this prompts for
1057 the version control system which the VC Directory buffer should use.
1062 @cindex CVS directory mode
1063 In addition to the VC Directory buffer, Emacs has a similar facility
1064 called PCL-CVS which is specialized for CVS. @xref{Top, , About
1065 PCL-CVS, pcl-cvs, PCL-CVS --- The Emacs Front-End to CVS}.
1069 * Buffer: VC Directory Buffer. What the buffer looks like and means.
1070 * Commands: VC Directory Commands. Commands to use in a VC directory buffer.
1073 @node VC Directory Buffer
1074 @subsubsection The VC Directory Buffer
1076 The VC Directory buffer contains a list of version-controlled files
1077 and their version control statuses. It lists files in the current
1078 directory (the one specified when you called @kbd{C-x v d}) and its
1079 subdirectories, but only those with a ``noteworthy'' status. Files
1080 that are up-to-date (i.e.@: the same as in the repository) are
1081 omitted. If all the files in a subdirectory are up-to-date, the
1082 subdirectory is not listed either. As an exception, if a file has
1083 become up-to-date as a direct result of a VC command, it is listed.
1085 Here is an example of a VC Directory buffer listing:
1092 unregistered temp.txt
1099 Two work files have been modified but not committed:
1100 @file{configure.ac} in the current directory, and @file{foo.c} in the
1101 @file{src/} subdirectory. The file named @file{README} has been added
1102 but is not yet committed, while @file{temp.txt} is not under version
1103 control (@pxref{Registering}).
1105 The @samp{*} characters next to the entries for @file{README} and
1106 @file{src/main.c} indicate that the user has marked out these files as
1107 the current VC fileset
1112 (@pxref{VC Directory Commands}).
1115 The above example is typical for a decentralized version control
1116 system like Bazaar, Git, or Mercurial. Other systems can show other
1117 statuses. For instance, CVS shows the @samp{needs-update} status if
1118 the repository has changes that have not been applied to the work
1119 file. RCS and SCCS show the name of the user locking a file as its
1123 @vindex vc-stay-local
1124 @vindex vc-cvs-stay-local
1125 On CVS and Subversion, the @code{vc-dir} command normally contacts
1126 the repository, which may be on a remote machine, to check for
1127 updates. If you change the variable @code{vc-stay-local} or
1128 @code{vc-cvs-stay-local} (for CVS) to @code{nil} (@pxref{CVS
1129 Options}), then Emacs avoids contacting a remote repository when
1130 generating the VC Directory buffer (it will still contact it when
1131 necessary, e.g.@: when doing a commit). This may be desirable if you
1132 are working offline or the network is slow.
1135 @vindex vc-directory-exclusion-list
1136 The VC Directory buffer omits subdirectories listed in the variable
1137 @code{vc-directory-exclusion-list}. Its default value contains
1138 directories that are used internally by version control systems.
1140 @node VC Directory Commands
1141 @subsubsection VC Directory Commands
1143 Emacs provides several commands for navigating the VC Directory
1144 buffer, and for ``marking'' files as belonging to the current VC
1150 Move point to the next entry (@code{vc-dir-next-line}).
1153 Move point to the previous entry (@code{vc-dir-previous-line}).
1156 Move to the next directory entry (@code{vc-dir-next-directory}).
1159 Move to the previous directory entry
1160 (@code{vc-dir-previous-directory}).
1164 Visit the file or directory listed on the current line
1165 (@code{vc-dir-find-file}).
1168 Visit the file or directory on the current line, in a separate window
1169 (@code{vc-dir-find-file-other-window}).
1172 Mark the file or directory on the current line (@code{vc-dir-mark}),
1173 putting it in the current VC fileset. If the region is active, mark
1174 all files in the region.
1176 A file cannot be marked with this command if it is already in a marked
1177 directory, or one of its subdirectories. Similarly, a directory
1178 cannot be marked with this command if any file in its tree is marked.
1181 If point is on a file entry, mark all files with the same status; if
1182 point is on a directory entry, mark all files in that directory tree
1183 (@code{vc-dir-mark-all-files}). With a prefix argument, mark all
1184 listed files and directories.
1186 @kindex q @r{(VC Directory)}
1189 Bury the VC Directory buffer, and delete its window if the window was
1190 created just for that buffer.
1193 Unmark the file or directory on the current line. If the region is
1194 active, unmark all the files in the region (@code{vc-dir-unmark}).
1197 If point is on a file entry, unmark all files with the same status; if
1198 point is on a directory entry, unmark all files in that directory tree
1199 (@code{vc-dir-unmark-all-files}). With a prefix argument, unmark all
1200 files and directories.
1203 Hide files with @samp{up-to-date} status
1204 (@code{vc-dir-hide-up-to-date}).
1207 Quit the VC Directory buffer, and bury it (@code{quit-window}).
1211 @findex vc-dir-mark-all-files
1212 While in the VC Directory buffer, all the files that you mark with
1213 @kbd{m} (@code{vc-dir-mark}) or @kbd{M} (@code{vc-dir-mark}) are in
1214 the current VC fileset. If you mark a directory entry with @kbd{m},
1215 all the listed files in that directory tree are in the current VC
1216 fileset. The files and directories that belong to the current VC
1217 fileset are indicated with a @samp{*} character in the VC Directory
1218 buffer, next to their VC status. In this way, you can set up a
1219 multi-file VC fileset to be acted on by VC commands like @w{@kbd{C-x v
1220 v}} (@pxref{Basic VC Editing}), @w{@kbd{C-x v =}} (@pxref{Old
1221 Revisions}), and @w{@kbd{C-x v u}} (@pxref{VC Undo}).
1223 The VC Directory buffer also defines some single-key shortcuts for
1224 VC commands with the @kbd{C-x v} prefix: @kbd{=}, @kbd{+}, @kbd{l},
1225 @kbd{i}, and @kbd{v}.
1227 For example, you can commit a set of edited files by opening a VC
1228 Directory buffer, where the files are listed with the @samp{edited}
1229 status; marking the files; and typing @kbd{v} or @kbd{C-x v v}
1230 (@code{vc-next-action}). If the version control system is
1231 changeset-based, Emacs will commit the files in a single revision.
1233 While in the VC Directory buffer, you can also perform search and
1234 replace on the current VC fileset, with the following commands:
1238 Search the fileset (@code{vc-dir-search}).
1241 Do a regular expression query replace on the fileset
1242 (@code{vc-dir-query-replace-regexp}).
1245 Do an incremental search on the fileset (@code{vc-dir-isearch}).
1248 Do an incremental regular expression search on the fileset
1249 (@code{vc-dir-isearch-regexp}).
1253 Apart from acting on multiple files, these commands behave much like
1254 their single-buffer counterparts (@pxref{Search}).
1256 @cindex stashes in version control
1257 @cindex shelves in version control
1258 The above commands are also available via the menu bar, and via a
1259 context menu invoked by @kbd{Mouse-2}. Furthermore, some VC backends
1260 use the menu to provide extra backend-specific commands. For example,
1261 Git and Bazaar allow you to manipulate @dfn{stashes} and @dfn{shelves}
1262 (where are a way to temporarily put aside uncommitted changes, and
1263 bring them back at a later time).
1266 @subsection Version Control Branches
1267 @cindex branch (version control)
1269 One use of version control is to support multiple independent lines
1270 of development, which are called @dfn{branches}. Branches are used
1271 for maintaining separate ``stable'' and ``development'' versions of a
1272 program, and for developing unrelated features in isolation from one
1275 VC's support for branch operations is currently fairly limited. For
1276 decentralized version control systems, it provides commands for
1277 @dfn{updating} one branch with the contents of another, and for
1278 @dfn{merging} the changes made to two different branches
1279 (@pxref{Merging}). For centralized version control systems, it
1280 supports checking out different branches and committing into new or
1284 * Switching Branches:: How to get to another existing branch.
1285 * VC Pull:: Updating the contents of a branch.
1286 * Merging:: Transferring changes between branches.
1287 * Creating Branches:: How to start a new branch.
1290 @node Switching Branches
1291 @subsubsection Switching between Branches
1293 The various version control systems differ in how branches are
1294 implemented, and these differences cannot be entirely concealed by VC.
1296 On some decentralized version control systems, including Bazaar and
1297 Mercurial in its normal mode of operation, each branch has its own
1298 working directory tree, so switching between branches just involves
1299 switching directories. On Git, switching between branches is done
1300 using the @command{git branch} command, which changes the contents of
1301 the working tree itself.
1303 On centralized version control systems, you can switch between
1304 branches by typing @kbd{C-u C-x v v} in an up-to-date work file
1305 (@pxref{Advanced C-x v v}), and entering the revision ID for a
1306 revision on another branch. On CVS, for instance, revisions on the
1307 @dfn{trunk} (the main line of development) normally have IDs of the
1308 form 1.1, 1.2, 1.3, @dots{}, while the first branch created from (say)
1309 revision 1.2 has revision IDs 1.2.1.1, 1.2.1.2, @dots{}, the second
1310 branch created from revision 1.2 has revision IDs 1.2.2.1, 1.2.2.2,
1311 @dots{}, and so forth. You can also specify the @dfn{branch ID},
1312 which is a branch revision ID omitting its final component
1313 (e.g.@: 1.2.1), to switch to the latest revision on that branch.
1315 On a locking-based system, switching to a different branch also
1316 unlocks (write-protects) the working tree.
1318 Once you have switched to a branch, VC commands will apply to that
1319 branch until you switch away; for instance, any VC filesets that you
1320 commit will be committed to that specific branch.
1323 @subsubsection Pulling Changes into a Branch
1327 On a decentralized version control system, update the current branch
1328 by ``pulling in'' changes from another location.
1330 On a centralized version control system, update the current VC
1336 On a decentralized version control system, the command @kbd{C-x v +}
1337 (@code{vc-pull}) updates the current branch and working tree. It is
1338 typically used to update a copy of a remote branch. If you supply a
1339 prefix argument, the command prompts for the exact version control
1340 command to use, which lets you specify where to pull changes from.
1341 Otherwise, it pulls from a default location determined by the version
1344 Amongst decentralized version control systems, @kbd{C-x v +} is
1345 currently supported only by Bazaar, Git, and Mercurial. On Bazaar, it
1346 calls @command{bzr pull} for ordinary branches (to pull from a master
1347 branch into a mirroring branch), and @command{bzr update} for a bound
1348 branch (to pull from a central repository). On Git, it calls
1349 @command{git pull} to fetch changes from a remote repository and merge
1350 it into the current branch. On Mercurial, it calls @command{hg pull
1351 -u} to fetch changesets from the default remote repository and update
1352 the working directory.
1354 Prior to pulling, you can use @kbd{C-x v I} (@code{vc-log-incoming})
1355 to view a log buffer of the changes to be applied. @xref{VC Change
1358 On a centralized version control system like CVS, @kbd{C-x v +}
1359 updates the current VC fileset from the repository.
1362 @subsubsection Merging Branches
1363 @cindex merging changes
1367 On a decentralized version control system, merge changes from another
1368 branch into the current one.
1370 On a centralized version control system, merge changes from another
1371 branch into the current VC fileset.
1374 While developing a branch, you may sometimes need to @dfn{merge} in
1375 changes that have already been made in another branch. This is not a
1376 trivial operation, as overlapping changes may have been made to the
1379 On a decentralized version control system, merging is done with the
1380 command @kbd{C-x v m} (@code{vc-merge}). On Bazaar, this prompts for
1381 the exact arguments to pass to @command{bzr merge}, offering a
1382 sensible default if possible. On Git, this prompts for the name of a
1383 branch to merge from, with completion (based on the branch names known
1384 to the current repository). The output from running the merge command
1385 is shown in a separate buffer.
1387 On a centralized version control system like CVS, @kbd{C-x v m}
1388 prompts for a branch ID, or a pair of revision IDs (@pxref{Switching
1389 Branches}); then it finds the changes from that branch, or the changes
1390 between the two revisions you specified, and merges those changes into
1391 the current VC fileset. If you just type @key{RET}, Emacs simply
1392 merges any changes that were made on the same branch since you checked
1396 @cindex resolving conflicts
1397 Immediately after performing a merge, only the working tree is
1398 modified, and you can review the changes produced by the merge with
1399 @kbd{C-x v D} and related commands (@pxref{Old Revisions}). If the
1400 two branches contained overlapping changes, merging produces a
1401 @dfn{conflict}; a warning appears in the output of the merge command,
1402 and @dfn{conflict markers} are inserted into each affected work file,
1403 surrounding the two sets of conflicting changes. You must then
1404 resolve the conflict by editing the conflicted files. Once you are
1405 done, the modified files must be committed in the usual way for the
1406 merge to take effect (@pxref{Basic VC Editing}).
1408 @node Creating Branches
1409 @subsubsection Creating New Branches
1411 On centralized version control systems like CVS, Emacs supports
1412 creating new branches as part of a commit operation. When committing
1413 a modified VC fileset, type @kbd{C-u C-x v v} (@code{vc-next-action}
1414 with a prefix argument; @pxref{Advanced C-x v v}). Then Emacs prompts
1415 for a revision ID for the new revision. You should specify a suitable
1416 branch ID for a branch starting at the current revision. For example,
1417 if the current revision is 2.5, the branch ID should be 2.5.1, 2.5.2,
1418 and so on, depending on the number of existing branches at that point.
1420 To create a new branch at an older revision (one that is no longer
1421 the head of a branch), first select that revision (@pxref{Switching
1422 Branches}). Your procedure will then differ depending on whether you
1423 are using a locking or merging-based VCS.
1425 On a locking VCS, you will need to lock the old revision branch with
1426 @kbd{C-x v v}. You'll be asked to confirm, when you lock the old
1427 revision, that you really mean to create a new branch---if you say no,
1428 you'll be offered a chance to lock the latest revision instead. On a
1429 merging-based VCS you will skip this step.
1431 Then make your changes and type @kbd{C-x v v} again to commit a new
1432 revision. This creates a new branch starting from the selected
1435 After the branch is created, subsequent commits create new revisions
1436 on that branch. To leave the branch, you must explicitly select a
1437 different revision with @kbd{C-u C-x v v}.
1440 @include vc1-xtra.texi
1444 @section Change Logs
1447 Many software projects keep a @dfn{change log}. This is a file,
1448 normally named @file{ChangeLog}, containing a chronological record of
1449 when and how the program was changed. Sometimes, there are several
1450 change log files, each recording the changes in one directory or
1454 * Change Log Commands:: Commands for editing change log files.
1455 * Format of ChangeLog:: What the change log file looks like.
1458 @node Change Log Commands
1459 @subsection Change Log Commands
1462 @findex add-change-log-entry-other-window
1463 The Emacs command @kbd{C-x 4 a} adds a new entry to the change log
1464 file for the file you are editing
1465 (@code{add-change-log-entry-other-window}). If that file is actually
1466 a backup file, it makes an entry appropriate for the file's
1467 parent---that is useful for making log entries for functions that
1468 have been deleted in the current version.
1470 @kbd{C-x 4 a} visits the change log file and creates a new entry
1471 unless the most recent entry is for today's date and your name. It
1472 also creates a new item for the current file. For many languages, it
1473 can even guess the name of the function or other object that was
1476 @vindex add-log-keep-changes-together
1477 When the variable @code{add-log-keep-changes-together} is
1478 non-@code{nil}, @kbd{C-x 4 a} adds to any existing item for the file
1479 rather than starting a new item.
1481 You can combine multiple changes of the same nature. If you don't
1482 enter any text after the initial @kbd{C-x 4 a}, any subsequent
1483 @kbd{C-x 4 a} adds another symbol to the change log entry.
1485 @vindex add-log-always-start-new-record
1486 If @code{add-log-always-start-new-record} is non-@code{nil},
1487 @kbd{C-x 4 a} always makes a new entry, even if the last entry
1488 was made by you and on the same date.
1490 @vindex change-log-version-info-enabled
1491 @vindex change-log-version-number-regexp-list
1492 @cindex file version in change log entries
1493 If the value of the variable @code{change-log-version-info-enabled}
1494 is non-@code{nil}, @kbd{C-x 4 a} adds the file's version number to the
1495 change log entry. It finds the version number by searching the first
1496 ten percent of the file, using regular expressions from the variable
1497 @code{change-log-version-number-regexp-list}.
1499 @cindex Change Log mode
1500 @findex change-log-mode
1501 The change log file is visited in Change Log mode. In this major
1502 mode, each bunch of grouped items counts as one paragraph, and each
1503 entry is considered a page. This facilitates editing the entries.
1504 @kbd{C-j} and auto-fill indent each new line like the previous line;
1505 this is convenient for entering the contents of an entry.
1507 You can use the @code{next-error} command (by default bound to
1508 @kbd{C-x `}) to move between entries in the Change Log, when Change
1509 Log mode is on. You will jump to the actual site in the file that was
1510 changed, not just to the next Change Log entry. You can also use
1511 @code{previous-error} to move back in the same list.
1513 @findex change-log-merge
1514 You can use the command @kbd{M-x change-log-merge} to merge other
1515 log files into a buffer in Change Log Mode, preserving the date
1516 ordering of entries.
1518 Version control systems are another way to keep track of changes in
1519 your program and keep a change log. In the VC log buffer, typing
1520 @kbd{C-c C-a} (@code{log-edit-insert-changelog}) inserts the relevant
1521 Change Log entry, if one exists. @xref{Log Buffer}.
1523 @node Format of ChangeLog
1524 @subsection Format of ChangeLog
1526 A change log entry starts with a header line that contains the
1527 current date, your name (taken from the variable
1528 @code{add-log-full-name}), and your email address (taken from the
1529 variable @code{add-log-mailing-address}). Aside from these header
1530 lines, every line in the change log starts with a space or a tab. The
1531 bulk of the entry consists of @dfn{items}, each of which starts with a
1532 line starting with whitespace and a star. Here are two entries, both
1533 dated in May 1993, with two items and one item respectively.
1539 1993-05-25 Richard Stallman <rms@@gnu.org>
1541 * man.el: Rename symbols `man-*' to `Man-*'.
1542 (manual-entry): Make prompt string clearer.
1544 * simple.el (blink-matching-paren-distance):
1545 Change default to 12,000.
1547 1993-05-24 Richard Stallman <rms@@gnu.org>
1549 * vc.el (minor-mode-map-alist): Don't use it if it's void.
1550 (vc-cancel-version): Doc fix.
1553 One entry can describe several changes; each change should have its
1554 own item, or its own line in an item. Normally there should be a
1555 blank line between items. When items are related (parts of the same
1556 change, in different places), group them by leaving no blank line
1559 You should put a copyright notice and permission notice at the
1560 end of the change log file. Here is an example:
1563 Copyright 1997, 1998 Free Software Foundation, Inc.
1564 Copying and distribution of this file, with or without modification, are
1565 permitted provided the copyright notice and this notice are preserved.
1569 Of course, you should substitute the proper years and copyright holder.
1572 @section Tags Tables
1573 @cindex tags and tag tables
1575 A @dfn{tag} is a reference to a subunit in a program or in a
1576 document. In source code, tags reference syntactic elements of the
1577 program: functions, subroutines, data types, macros, etc. In a
1578 document, tags reference chapters, sections, appendices, etc. Each
1579 tag specifies the name of the file where the corresponding subunit is
1580 defined, and the position of the subunit's definition in that file.
1582 A @dfn{tags table} records the tags extracted by scanning the source
1583 code of a certain program or a certain document. Tags extracted from
1584 generated files reference the original files, rather than the
1585 generated files that were scanned during tag extraction. Examples of
1586 generated files include C files generated from Cweb source files, from
1587 a Yacc parser, or from Lex scanner definitions; @file{.i} preprocessed
1588 C files; and Fortran files produced by preprocessing @file{.fpp}
1592 To produce a tags table, you run the @command{etags} shell command
1593 on a document or the source code file. The @samp{etags} program
1594 writes the tags to a @dfn{tags table file}, or @dfn{tags file} in
1595 short. The conventional name for a tags file is @file{TAGS}.
1596 @xref{Create Tags Table}.
1598 Emacs provides many commands for searching and replacing using the
1599 information recorded in tags tables. For instance, the @kbd{M-.}
1600 (@code{find-tag}) jumps to the location of a specified function
1601 definition in its source file. @xref{Find Tag}.
1603 @cindex C++ class browser, tags
1605 @cindex class browser, C++
1607 The Ebrowse facility is similar to @command{etags} but specifically
1608 tailored for C++. @xref{Top,, Ebrowse, ebrowse, Ebrowse User's
1609 Manual}. The Semantic package provides another way to generate and
1610 use tags, separate from the @command{etags} facility.
1614 * Tag Syntax:: Tag syntax for various types of code and text files.
1615 * Create Tags Table:: Creating a tags table with @command{etags}.
1616 * Etags Regexps:: Create arbitrary tags using regular expressions.
1617 * Select Tags Table:: How to visit a tags table.
1618 * Find Tag:: Commands to find the definition of a specific tag.
1619 * Tags Search:: Using a tags table for searching and replacing.
1620 * List Tags:: Using tags for completion, and listing them.
1624 @subsection Source File Tag Syntax
1626 Here is how tag syntax is defined for the most popular languages:
1630 In C code, any C function or typedef is a tag, and so are definitions of
1631 @code{struct}, @code{union} and @code{enum}.
1632 @code{#define} macro definitions, @code{#undef} and @code{enum}
1634 tags, unless you specify @samp{--no-defines} when making the tags table.
1635 Similarly, global variables are tags, unless you specify
1636 @samp{--no-globals}, and so are struct members, unless you specify
1637 @samp{--no-members}. Use of @samp{--no-globals}, @samp{--no-defines}
1638 and @samp{--no-members} can make the tags table file much smaller.
1640 You can tag function declarations and external variables in addition
1641 to function definitions by giving the @samp{--declarations} option to
1645 In C++ code, in addition to all the tag constructs of C code, member
1646 functions are also recognized; member variables are also recognized,
1647 unless you use the @samp{--no-members} option. Tags for variables and
1648 functions in classes are named @samp{@var{class}::@var{variable}} and
1649 @samp{@var{class}::@var{function}}. @code{operator} definitions have
1650 tag names like @samp{operator+}.
1653 In Java code, tags include all the constructs recognized in C++, plus
1654 the @code{interface}, @code{extends} and @code{implements} constructs.
1655 Tags for variables and functions in classes are named
1656 @samp{@var{class}.@var{variable}} and @samp{@var{class}.@var{function}}.
1659 In La@TeX{} documents, the arguments for @code{\chapter},
1660 @code{\section}, @code{\subsection}, @code{\subsubsection},
1661 @code{\eqno}, @code{\label}, @code{\ref}, @code{\cite},
1662 @code{\bibitem}, @code{\part}, @code{\appendix}, @code{\entry},
1663 @code{\index}, @code{\def}, @code{\newcommand}, @code{\renewcommand},
1664 @code{\newenvironment} and @code{\renewenvironment} are tags.
1666 Other commands can make tags as well, if you specify them in the
1667 environment variable @env{TEXTAGS} before invoking @command{etags}. The
1668 value of this environment variable should be a colon-separated list of
1669 command names. For example,
1672 TEXTAGS="mycommand:myothercommand"
1677 specifies (using Bourne shell syntax) that the commands
1678 @samp{\mycommand} and @samp{\myothercommand} also define tags.
1681 In Lisp code, any function defined with @code{defun}, any variable
1682 defined with @code{defvar} or @code{defconst}, and in general the first
1683 argument of any expression that starts with @samp{(def} in column zero is
1687 In Scheme code, tags include anything defined with @code{def} or with a
1688 construct whose name starts with @samp{def}. They also include variables
1689 set with @code{set!} at top level in the file.
1692 Several other languages are also supported:
1697 In Ada code, functions, procedures, packages, tasks and types are
1698 tags. Use the @samp{--packages-only} option to create tags for
1701 In Ada, the same name can be used for different kinds of entity
1702 (e.g.@:, for a procedure and for a function). Also, for things like
1703 packages, procedures and functions, there is the spec (i.e.@: the
1704 interface) and the body (i.e.@: the implementation). To make it
1705 easier to pick the definition you want, Ada tag name have suffixes
1706 indicating the type of entity:
1723 Thus, @kbd{M-x find-tag @key{RET} bidule/b @key{RET}} will go
1724 directly to the body of the package @code{bidule}, while @kbd{M-x
1725 find-tag @key{RET} bidule @key{RET}} will just search for any tag
1729 In assembler code, labels appearing at the beginning of a line,
1730 followed by a colon, are tags.
1733 In Bison or Yacc input files, each rule defines as a tag the nonterminal
1734 it constructs. The portions of the file that contain C code are parsed
1738 In Cobol code, tags are paragraph names; that is, any word starting in
1739 column 8 and followed by a period.
1742 In Erlang code, the tags are the functions, records and macros defined
1746 In Fortran code, functions, subroutines and block data are tags.
1749 In HTML input files, the tags are the @code{title} and the @code{h1},
1750 @code{h2}, @code{h3} headers. Also, tags are @code{name=} in anchors
1751 and all occurrences of @code{id=}.
1754 In Lua input files, all functions are tags.
1757 In makefiles, targets are tags; additionally, variables are tags
1758 unless you specify @samp{--no-globals}.
1761 In Objective C code, tags include Objective C definitions for classes,
1762 class categories, methods and protocols. Tags for variables and
1763 functions in classes are named @samp{@var{class}::@var{variable}} and
1764 @samp{@var{class}::@var{function}}.
1767 In Pascal code, the tags are the functions and procedures defined in
1771 In Perl code, the tags are the packages, subroutines and variables
1772 defined by the @code{package}, @code{sub}, @code{my} and @code{local}
1773 keywords. Use @samp{--globals} if you want to tag global variables.
1774 Tags for subroutines are named @samp{@var{package}::@var{sub}}. The
1775 name for subroutines defined in the default package is
1776 @samp{main::@var{sub}}.
1779 In PHP code, tags are functions, classes and defines. Vars are tags
1780 too, unless you use the @samp{--no-members} option.
1783 In PostScript code, the tags are the functions.
1786 In Prolog code, tags are predicates and rules at the beginning of
1790 In Python code, @code{def} or @code{class} at the beginning of a line
1794 You can also generate tags based on regexp matching (@pxref{Etags
1795 Regexps}) to handle other formats and languages.
1797 @node Create Tags Table
1798 @subsection Creating Tags Tables
1799 @cindex @command{etags} program
1801 The @command{etags} program is used to create a tags table file. It knows
1802 the syntax of several languages, as described in
1804 the previous section.
1809 Here is how to run @command{etags}:
1812 etags @var{inputfiles}@dots{}
1816 The @command{etags} program reads the specified files, and writes a tags
1817 table named @file{TAGS} in the current working directory. You can
1818 optionally specify a different file name for the tags table by using the
1819 @samp{--output=@var{file}} option; specifying @file{-} as a file name
1820 prints the tags table to standard output.
1822 If the specified files don't exist, @command{etags} looks for
1823 compressed versions of them and uncompresses them to read them. Under
1824 MS-DOS, @command{etags} also looks for file names like @file{mycode.cgz}
1825 if it is given @samp{mycode.c} on the command line and @file{mycode.c}
1828 If the tags table becomes outdated due to changes in the files
1829 described in it, you can update it by running the @command{etags}
1830 program again. If the tags table does not record a tag, or records it
1831 for the wrong file, then Emacs will not be able to find that
1832 definition until you update the tags table. But if the position
1833 recorded in the tags table becomes a little bit wrong (due to other
1834 editing), Emacs will still be able to find the right position, with a
1837 Thus, there is no need to update the tags table after each edit.
1838 You should update a tags table when you define new tags that you want
1839 to have listed, or when you move tag definitions from one file to
1840 another, or when changes become substantial.
1842 You can make a tags table @dfn{include} another tags table, by
1843 passing the @samp{--include=@var{file}} option to @command{etags}. It
1844 then covers all the files covered by the included tags file, as well
1847 If you specify the source files with relative file names when you run
1848 @command{etags}, the tags file will contain file names relative to the
1849 directory where the tags file was initially written. This way, you can
1850 move an entire directory tree containing both the tags file and the
1851 source files, and the tags file will still refer correctly to the source
1852 files. If the tags file is @file{-} or is in the @file{/dev} directory,
1853 however, the file names are
1854 made relative to the current working directory. This is useful, for
1855 example, when writing the tags to @file{/dev/stdout}.
1857 When using a relative file name, it should not be a symbolic link
1858 pointing to a tags file in a different directory, because this would
1859 generally render the file names invalid.
1861 If you specify absolute file names as arguments to @command{etags}, then
1862 the tags file will contain absolute file names. This way, the tags file
1863 will still refer to the same files even if you move it, as long as the
1864 source files remain in the same place. Absolute file names start with
1865 @samp{/}, or with @samp{@var{device}:/} on MS-DOS and MS-Windows.
1867 When you want to make a tags table from a great number of files,
1868 you may have problems listing them on the command line, because some
1869 systems have a limit on its length. You can circumvent this limit by
1870 telling @command{etags} to read the file names from its standard
1871 input, by typing a dash in place of the file names, like this:
1874 find . -name "*.[chCH]" -print | etags -
1877 @command{etags} recognizes the language used in an input file based
1878 on its file name and contents. You can specify the language
1879 explicitly with the @samp{--language=@var{name}} option. You can
1880 intermix these options with file names; each one applies to the file
1881 names that follow it. Specify @samp{--language=auto} to tell
1882 @command{etags} to resume guessing the language from the file names
1883 and file contents. Specify @samp{--language=none} to turn off
1884 language-specific processing entirely; then @command{etags} recognizes
1885 tags by regexp matching alone (@pxref{Etags Regexps}).
1887 The option @samp{--parse-stdin=@var{file}} is mostly useful when
1888 calling @command{etags} from programs. It can be used (only once) in
1889 place of a file name on the command line. @command{etags} will read from
1890 standard input and mark the produced tags as belonging to the file
1893 @samp{etags --help} outputs the list of the languages @command{etags}
1894 knows, and the file name rules for guessing the language. It also prints
1895 a list of all the available @command{etags} options, together with a short
1896 explanation. If followed by one or more @samp{--language=@var{lang}}
1897 options, it outputs detailed information about how tags are generated for
1901 @subsection Etags Regexps
1903 The @samp{--regex} option to @command{etags} allows tags to be
1904 recognized by regular expression matching. You can intermix this
1905 option with file names; each one applies to the source files that
1906 follow it. If you specify multiple @samp{--regex} options, all of
1907 them are used in parallel. The syntax is:
1910 --regex=[@var{@{language@}}]/@var{tagregexp}/[@var{nameregexp}/]@var{modifiers}
1914 The essential part of the option value is @var{tagregexp}, the regexp
1915 for matching tags. It is always used anchored, that is, it only
1916 matches at the beginning of a line. If you want to allow indented
1917 tags, use a regexp that matches initial whitespace; start it with
1920 In these regular expressions, @samp{\} quotes the next character, and
1921 all the GCC character escape sequences are supported (@samp{\a} for
1922 bell, @samp{\b} for back space, @samp{\d} for delete, @samp{\e} for
1923 escape, @samp{\f} for formfeed, @samp{\n} for newline, @samp{\r} for
1924 carriage return, @samp{\t} for tab, and @samp{\v} for vertical tab).
1926 Ideally, @var{tagregexp} should not match more characters than are
1927 needed to recognize what you want to tag. If the syntax requires you
1928 to write @var{tagregexp} so it matches more characters beyond the tag
1929 itself, you should add a @var{nameregexp}, to pick out just the tag.
1930 This will enable Emacs to find tags more accurately and to do
1931 completion on tag names more reliably. You can find some examples
1934 The @var{modifiers} are a sequence of zero or more characters that
1935 modify the way @command{etags} does the matching. A regexp with no
1936 modifiers is applied sequentially to each line of the input file, in a
1937 case-sensitive way. The modifiers and their meanings are:
1941 Ignore case when matching this regexp.
1943 Match this regular expression against the whole file, so that
1944 multi-line matches are possible.
1946 Match this regular expression against the whole file, and allow
1947 @samp{.} in @var{tagregexp} to match newlines.
1950 The @samp{-R} option cancels all the regexps defined by preceding
1951 @samp{--regex} options. It too applies to the file names following
1952 it. Here's an example:
1955 etags --regex=/@var{reg1}/i voo.doo --regex=/@var{reg2}/m \
1956 bar.ber -R --lang=lisp los.er
1960 Here @command{etags} chooses the parsing language for @file{voo.doo} and
1961 @file{bar.ber} according to their contents. @command{etags} also uses
1962 @var{reg1} to recognize additional tags in @file{voo.doo}, and both
1963 @var{reg1} and @var{reg2} to recognize additional tags in
1964 @file{bar.ber}. @var{reg1} is checked against each line of
1965 @file{voo.doo} and @file{bar.ber}, in a case-insensitive way, while
1966 @var{reg2} is checked against the whole @file{bar.ber} file,
1967 permitting multi-line matches, in a case-sensitive way. @command{etags}
1968 uses only the Lisp tags rules, with no user-specified regexp matching,
1969 to recognize tags in @file{los.er}.
1971 You can restrict a @samp{--regex} option to match only files of a
1972 given language by using the optional prefix @var{@{language@}}.
1973 (@samp{etags --help} prints the list of languages recognized by
1974 @command{etags}.) This is particularly useful when storing many
1975 predefined regular expressions for @command{etags} in a file. The
1976 following example tags the @code{DEFVAR} macros in the Emacs source
1977 files, for the C language only:
1980 --regex='@{c@}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/'
1984 When you have complex regular expressions, you can store the list of
1985 them in a file. The following option syntax instructs @command{etags} to
1986 read two files of regular expressions. The regular expressions
1987 contained in the second file are matched without regard to case.
1990 --regex=@@@var{case-sensitive-file} --ignore-case-regex=@@@var{ignore-case-file}
1994 A regex file for @command{etags} contains one regular expression per
1995 line. Empty lines, and lines beginning with space or tab are ignored.
1996 When the first character in a line is @samp{@@}, @command{etags} assumes
1997 that the rest of the line is the name of another file of regular
1998 expressions; thus, one such file can include another file. All the
1999 other lines are taken to be regular expressions. If the first
2000 non-whitespace text on the line is @samp{--}, that line is a comment.
2002 For example, we can create a file called @samp{emacs.tags} with the
2006 -- This is for GNU Emacs C source files
2007 @{c@}/[ \t]*DEFVAR_[A-Z_ \t(]+"\([^"]+\)"/\1/
2011 and then use it like this:
2014 etags --regex=@@emacs.tags *.[ch] */*.[ch]
2017 Here are some more examples. The regexps are quoted to protect them
2018 from shell interpretation.
2026 etags --language=none \
2027 --regex='/[ \t]*function.*=[ \t]*\([^ \t]*\)[ \t]*(/\1/' \
2028 --regex='/###key \(.*\)/\1/' \
2029 --regex='/[ \t]*global[ \t].*/' \
2034 Note that tags are not generated for scripts, so that you have to add
2035 a line by yourself of the form @samp{###key @var{scriptname}} if you
2042 etags --language=none --regex='/proc[ \t]+\([^ \t]+\)/\1/' *.tcl
2049 etags --language=none \
2050 --regex='/[ \t]*\(ARCHITECTURE\|CONFIGURATION\) +[^ ]* +OF/' \
2051 --regex='/[ \t]*\(ATTRIBUTE\|ENTITY\|FUNCTION\|PACKAGE\
2052 \( BODY\)?\|PROCEDURE\|PROCESS\|TYPE\)[ \t]+\([^ \t(]+\)/\3/'
2056 @node Select Tags Table
2057 @subsection Selecting a Tags Table
2059 @findex visit-tags-table
2060 Emacs has at any time one @dfn{selected} tags table. All the
2061 commands for working with tags tables use the selected one. To select
2062 a tags table, type @kbd{M-x visit-tags-table}, which reads the tags
2063 table file name as an argument, with @file{TAGS} in the default
2064 directory as the default.
2066 @vindex tags-file-name
2067 Emacs does not actually read in the tags table contents until you
2068 try to use them; all @code{visit-tags-table} does is store the file
2069 name in the variable @code{tags-file-name}, and setting the variable
2070 yourself is just as good. The variable's initial value is @code{nil};
2071 that value tells all the commands for working with tags tables that
2072 they must ask for a tags table file name to use.
2074 Using @code{visit-tags-table} when a tags table is already loaded
2075 gives you a choice: you can add the new tags table to the current list
2076 of tags tables, or start a new list. The tags commands use all the tags
2077 tables in the current list. If you start a new list, the new tags table
2078 is used @emph{instead} of others. If you add the new table to the
2079 current list, it is used @emph{as well as} the others.
2081 @vindex tags-table-list
2082 You can specify a precise list of tags tables by setting the variable
2083 @code{tags-table-list} to a list of strings, like this:
2085 @c keep this on two lines for formatting in smallbook
2088 (setq tags-table-list
2089 '("~/emacs" "/usr/local/lib/emacs/src"))
2094 This tells the tags commands to look at the @file{TAGS} files in your
2095 @file{~/emacs} directory and in the @file{/usr/local/lib/emacs/src}
2096 directory. The order depends on which file you are in and which tags
2097 table mentions that file, as explained above.
2099 Do not set both @code{tags-file-name} and @code{tags-table-list}.
2102 @subsection Finding a Tag
2104 The most important thing that a tags table enables you to do is to find
2105 the definition of a specific tag.
2108 @item M-.@: @var{tag} @key{RET}
2109 Find first definition of @var{tag} (@code{find-tag}).
2111 Find next alternate definition of last tag specified.
2113 Go back to previous tag found.
2114 @item C-M-. @var{pattern} @key{RET}
2115 Find a tag whose name matches @var{pattern} (@code{find-tag-regexp}).
2117 Find the next tag whose name matches the last pattern used.
2118 @item C-x 4 .@: @var{tag} @key{RET}
2119 Find first definition of @var{tag}, but display it in another window
2120 (@code{find-tag-other-window}).
2121 @item C-x 5 .@: @var{tag} @key{RET}
2122 Find first definition of @var{tag}, and create a new frame to select the
2123 buffer (@code{find-tag-other-frame}).
2125 Pop back to where you previously invoked @kbd{M-.} and friends.
2130 @kbd{M-.}@: (@code{find-tag}) prompts for a tag name and jumps to
2131 its source definition. It works by searching through the tags table
2132 for that tag's file and approximate character position, visiting that
2133 file, and searching for the tag definition at ever-increasing
2134 distances away from the recorded approximate position.
2136 When entering the tag argument to @kbd{M-.}, the usual minibuffer
2137 completion commands can be used (@pxref{Completion}), with the tag
2138 names in the selected tags table as completion candidates. If you
2139 specify an empty argument, the balanced expression in the buffer
2140 before or around point is the default argument. @xref{Expressions}.
2142 You don't need to give @kbd{M-.} the full name of the tag; a part
2143 will do. @kbd{M-.} finds tags which contain that argument as a
2144 substring. However, it prefers an exact match to a substring match.
2145 To find other tags that match the same substring, give @code{find-tag}
2146 a numeric argument, as in @kbd{C-u M-.} or @kbd{M-0 M-.}; this does
2147 not read a tag name, but continues searching the tags table's text for
2148 another tag containing the same substring last used.
2151 @findex find-tag-other-window
2153 @findex find-tag-other-frame
2154 Like most commands that can switch buffers, @code{find-tag} has a
2155 variant that displays the new buffer in another window, and one that
2156 makes a new frame for it. The former is @w{@kbd{C-x 4 .}}
2157 (@code{find-tag-other-window}), and the latter is @w{@kbd{C-x 5 .}}
2158 (@code{find-tag-other-frame}).
2160 To move back to previous tag definitions, use @kbd{C-u - M-.}; more
2161 generally, @kbd{M-.} with a negative numeric argument. Similarly,
2162 @w{@kbd{C-x 4 .}} with a negative argument finds the previous tag
2163 location in another window.
2166 @findex pop-tag-mark
2167 @vindex find-tag-marker-ring-length
2168 As well as going back to places you've found tags recently, you can
2169 go back to places @emph{from where} you found them, using @kbd{M-*}
2170 (@code{pop-tag-mark}). Thus you can find and examine the definition
2171 of something with @kbd{M-.} and then return to where you were with
2174 Both @kbd{C-u - M-.} and @kbd{M-*} allow you to retrace your steps to
2175 a depth determined by the variable @code{find-tag-marker-ring-length}.
2177 @findex find-tag-regexp
2179 The command @kbd{C-M-.} (@code{find-tag-regexp}) visits the tags that
2180 match a specified regular expression. It is just like @kbd{M-.} except
2181 that it does regexp matching instead of substring matching.
2184 @subsection Searching and Replacing with Tags Tables
2185 @cindex search and replace in multiple files
2186 @cindex multiple-file search and replace
2188 The commands in this section visit and search all the files listed
2189 in the selected tags table, one by one. For these commands, the tags
2190 table serves only to specify a sequence of files to search. These
2191 commands scan the list of tags tables starting with the first tags
2192 table (if any) that describes the current file, proceed from there to
2193 the end of the list, and then scan from the beginning of the list
2194 until they have covered all the tables in the list.
2197 @item M-x tags-search @key{RET} @var{regexp} @key{RET}
2198 Search for @var{regexp} through the files in the selected tags
2200 @item M-x tags-query-replace @key{RET} @var{regexp} @key{RET} @var{replacement} @key{RET}
2201 Perform a @code{query-replace-regexp} on each file in the selected tags table.
2203 Restart one of the commands above, from the current location of point
2204 (@code{tags-loop-continue}).
2208 @kbd{M-x tags-search} reads a regexp using the minibuffer, then
2209 searches for matches in all the files in the selected tags table, one
2210 file at a time. It displays the name of the file being searched so you
2211 can follow its progress. As soon as it finds an occurrence,
2212 @code{tags-search} returns.
2215 @findex tags-loop-continue
2216 Having found one match, you probably want to find all the rest.
2217 Type @kbd{M-,} (@code{tags-loop-continue}) to resume the
2218 @code{tags-search}, finding one more match. This searches the rest of
2219 the current buffer, followed by the remaining files of the tags table.
2221 @findex tags-query-replace
2222 @kbd{M-x tags-query-replace} performs a single
2223 @code{query-replace-regexp} through all the files in the tags table. It
2224 reads a regexp to search for and a string to replace with, just like
2225 ordinary @kbd{M-x query-replace-regexp}. It searches much like @kbd{M-x
2226 tags-search}, but repeatedly, processing matches according to your
2227 input. @xref{Replace}, for more information on query replace.
2229 @vindex tags-case-fold-search
2230 @cindex case-sensitivity and tags search
2231 You can control the case-sensitivity of tags search commands by
2232 customizing the value of the variable @code{tags-case-fold-search}. The
2233 default is to use the same setting as the value of
2234 @code{case-fold-search} (@pxref{Search Case}).
2236 It is possible to get through all the files in the tags table with a
2237 single invocation of @kbd{M-x tags-query-replace}. But often it is
2238 useful to exit temporarily, which you can do with any input event that
2239 has no special query replace meaning. You can resume the query
2240 replace subsequently by typing @kbd{M-,}; this command resumes the
2241 last tags search or replace command that you did. For instance, to
2242 skip the rest of the current file, you can type @kbd{M-> M-,}.
2244 The commands in this section carry out much broader searches than the
2245 @code{find-tag} family. The @code{find-tag} commands search only for
2246 definitions of tags that match your substring or regexp. The commands
2247 @code{tags-search} and @code{tags-query-replace} find every occurrence
2248 of the regexp, as ordinary search commands and replace commands do in
2251 These commands create buffers only temporarily for the files that they
2252 have to search (those which are not already visited in Emacs buffers).
2253 Buffers in which no match is found are quickly killed; the others
2256 As an alternative to @code{tags-search}, you can run @command{grep}
2257 as a subprocess and have Emacs show you the matching lines one by one.
2258 @xref{Grep Searching}.
2261 @subsection Tags Table Inquiries
2266 Perform completion on the text around point, using the selected tags
2267 table if one is loaded (@code{completion-at-point}).
2268 @item M-x list-tags @key{RET} @var{file} @key{RET}
2269 Display a list of the tags defined in the program file @var{file}.
2270 @item M-x tags-apropos @key{RET} @var{regexp} @key{RET}
2271 Display a list of all tags matching @var{regexp}.
2274 @cindex completion (symbol names)
2275 In most programming language modes, you can type @kbd{C-M-i} or
2276 @kbd{M-@key{TAB}} (@code{completion-at-point}) to complete the symbol
2277 at point. If there is a selected tags table, this command can use it
2278 to generate completion candidates. @xref{Symbol Completion}.
2281 @kbd{M-x list-tags} reads the name of one of the files covered by
2282 the selected tags table, and displays a list of tags defined in that
2283 file. Do not include a directory as part of the file name unless the
2284 file name recorded in the tags table includes a directory.
2286 @findex tags-apropos
2287 @vindex tags-apropos-verbose
2288 @vindex tags-tag-face
2289 @vindex tags-apropos-additional-actions
2290 @kbd{M-x tags-apropos} is like @code{apropos} for tags
2291 (@pxref{Apropos}). It displays a list of tags in the selected tags
2292 table whose entries match @var{regexp}. If the variable
2293 @code{tags-apropos-verbose} is non-@code{nil}, it displays the names
2294 of the tags files together with the tag names. You can customize the
2295 appearance of the output by setting the variable @code{tags-tag-face}
2296 to a face. You can display additional output by customizing the
2297 variable @code{tags-apropos-additional-actions}; see its documentation
2301 @kbd{M-x next-file} visits files covered by the selected tags table.
2302 The first time it is called, it visits the first file covered by the
2303 table. Each subsequent call visits the next covered file, unless a
2304 prefix argument is supplied, in which case it returns to the first
2308 @section Emacs Development Environment
2309 @cindex EDE (Emacs Development Environment)
2310 @cindex Emacs Development Environment
2311 @cindex Integrated development environment
2313 EDE (@dfn{Emacs Development Environment}) is a package that simplifies
2314 the task of creating, building, and debugging large programs with
2315 Emacs. It provides some of the features of an IDE, or @dfn{Integrated
2316 Development Environment}, in Emacs.
2318 This section provides a brief description of EDE usage.
2320 For full details, see @ref{Top, EDE,, ede, Emacs Development Environment}.
2323 For full details on Ede, type @kbd{C-h i} and then select the EDE
2327 EDE is implemented as a global minor mode (@pxref{Minor Modes}). To
2328 enable it, type @kbd{M-x global-ede-mode} or click on the
2329 @samp{Project Support (EDE)} item in the @samp{Tools} menu. You can
2330 also enable EDE each time you start Emacs, by adding the following
2331 line to your initialization file:
2338 Activating EDE adds a menu named @samp{Development} to the menu bar.
2339 Many EDE commands, including the ones described below, can be invoked
2342 EDE organizes files into @dfn{projects}, which correspond to
2343 directory trees. The @dfn{project root} is the topmost directory of a
2344 project. To define a new project, visit a file in the desired project
2345 root and type @kbd{M-x ede-new}. This command prompts for a
2346 @dfn{project type}, which refers to the underlying method that EDE
2347 will use to manage the project (@pxref{Creating a Project, EDE,, ede,
2348 Emacs Development Environment}). The most common project types are
2349 @samp{Make}, which uses Makefiles, and @samp{Automake}, which uses GNU
2350 Automake (@pxref{Top, Automake,, automake, Automake}). In both cases,
2351 EDE also creates a file named @file{Project.ede}, which stores
2352 information about the project.
2354 A project may contain one or more @dfn{targets}. A target can be an
2355 object file, executable program, or some other type of file, which is
2356 ``built'' from one or more of the files in the project.
2358 To add a new @dfn{target} to a project, type @kbd{C-c . t}
2359 (@code{M-x ede-new-target}). This command also asks if you wish to
2360 ``add'' the current file to that target, which means that the target
2361 is to be built from that file. After you have defined a target, you
2362 can add more files to it by typing @kbd{C-c . a}
2363 (@code{ede-add-file}).
2365 To build a target, type @kbd{C-c . c} (@code{ede-compile-target}).
2366 To build all the targets in the project, type @kbd{C-c . C}
2367 (@code{ede-compile-project}). EDE uses the file types to guess how
2368 the target should be built.
2371 @include emerge-xtra.texi