@c This is part of the Emacs manual.
-@c Copyright (C) 1985,86,87,93,94,95,97,99,00,2001 Free Software Foundation, Inc.
+@c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 1999, 2000,
+@c 2001, 2002, 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Maintaining, Abbrevs, Building, Top
-@chapter Maintaining Programs
-@cindex Lisp editing
-@cindex C editing
-@cindex program editing
+@chapter Maintaining Large Programs
- This chapter describes Emacs features for maintaining programs. The
-version control features,described in the chapter on files
-(@pxref{Version Control}), are also useful particularly for this
-purpose.
+ This chapter describes Emacs features for maintaining large
+programs. The version control features (@pxref{Version Control}) are
+also particularly useful for this purpose.
@menu
* Change Log:: Maintaining a change history for your program.
-* Authors:: Maintaining an @file{AUTHORS} file.
+* Format of ChangeLog:: What the change log file looks like.
* Tags:: Go direct to any function in your program in one
command. Tags remembers which file it is in.
-* Emerge:: A convenient way of merging two versions of a program.
+@ifnottex
+* Emerge:: A convenient way of merging two versions of a program.
+@end ifnottex
@end menu
@node Change Log
@section Change Logs
+ A change log file contains a chronological record of when and why you
+have changed a program, consisting of a sequence of entries describing
+individual changes. Normally it is kept in a file called
+@file{ChangeLog} in the same directory as the file you are editing, or
+one of its parent directories. A single @file{ChangeLog} file can
+record changes for all the files in its directory and all its
+subdirectories.
+
@cindex change log
@kindex C-x 4 a
@findex add-change-log-entry-other-window
parent---that is useful for making log entries for functions that
have been deleted in the current version.
- A change log file contains a chronological record of when and why you
-have changed a program, consisting of a sequence of entries describing
-individual changes. Normally it is kept in a file called
-@file{ChangeLog} in the same directory as the file you are editing, or
-one of its parent directories. A single @file{ChangeLog} file can
-record changes for all the files in its directory and all its
-subdirectories.
-
- A change log entry starts with a header line that contains the
-current date, your name, and your email address (taken from the
-variable @code{user-mail-address}). Aside from these header lines,
-every line in the change log starts with a space or a tab. The bulk
-of the entry consists of @dfn{items}, each of which starts with a line
-starting with whitespace and a star. Here are two entries, both dated
-in May 1993, each with two items:
-
-@iftex
-@medbreak
-@end iftex
-@smallexample
-1993-05-25 Richard Stallman <rms@@gnu.org>
-
- * man.el: Rename symbols `man-*' to `Man-*'.
- (manual-entry): Make prompt string clearer.
-
- * simple.el (blink-matching-paren-distance):
- Change default to 12,000.
-
-1993-05-24 Richard Stallman <rms@@gnu.org>
-
- * vc.el (minor-mode-map-alist): Don't use it if it's void.
- (vc-cancel-version): Doc fix.
-@end smallexample
-
- One entry can describe several changes; each change should have its
-own item. Normally there should be a blank line between items. When
-items are related (parts of the same change, in different places), group
-them by leaving no blank line between them. The second entry above
-contains two items grouped in this way.
-
@kbd{C-x 4 a} visits the change log file and creates a new entry
unless the most recent entry is for today's date and your name. It
also creates a new item for the current file. For many languages, it
changed.
@vindex add-log-keep-changes-together
- When the option @code{add-log-keep-changes-together} is
-non-@code{nil}, @kbd{C-x 4 a} adds to any existing entry for the file
-rather than starting a new entry.
+ When the variable @code{add-log-keep-changes-together} is
+non-@code{nil}, @kbd{C-x 4 a} adds to any existing item for the file
+rather than starting a new item.
+
+@vindex add-log-always-start-new-record
+ If @code{add-log-always-start-new-record} is non-@code{nil},
+@kbd{C-x 4 a} always makes a new entry, even if the last entry
+was made by you and on the same date.
@vindex change-log-version-info-enabled
@vindex change-log-version-number-regexp-list
log files into a buffer in Change Log Mode, preserving the date
ordering of entries.
-@findex change-log-redate
-@cindex converting change log date style
- Versions of Emacs before 20.1 used a different format for the time of
-the change log entry:
+ Version control systems are another way to keep track of changes in your
+program and keep a change log. @xref{Log Buffer}.
+
+@node Format of ChangeLog
+@section Format of ChangeLog
+
+ A change log entry starts with a header line that contains the current
+date, your name, and your email address (taken from the variable
+@code{add-log-mailing-address}). Aside from these header lines, every
+line in the change log starts with a space or a tab. The bulk of the
+entry consists of @dfn{items}, each of which starts with a line starting
+with whitespace and a star. Here are two entries, both dated in May
+1993, with two items and one item respectively.
+@iftex
+@medbreak
+@end iftex
@smallexample
-Fri May 25 11:23:23 1993 Richard Stallman <rms@@gnu.org>
+1993-05-25 Richard Stallman <rms@@gnu.org>
+
+ * man.el: Rename symbols `man-*' to `Man-*'.
+ (manual-entry): Make prompt string clearer.
+
+ * simple.el (blink-matching-paren-distance):
+ Change default to 12,000.
+
+1993-05-24 Richard Stallman <rms@@gnu.org>
+
+ * vc.el (minor-mode-map-alist): Don't use it if it's void.
+ (vc-cancel-version): Doc fix.
@end smallexample
-@noindent
-The @kbd{M-x change-log-redate} command converts all the old-style
-date entries in the change log file visited in the current buffer to
-the new format, to make the file uniform in style. This is handy when
-entries are contributed by many different people, some of whom use old
-versions of Emacs.
+ One entry can describe several changes; each change should have its
+own item, or its own line in an item. Normally there should be a
+blank line between items. When items are related (parts of the same
+change, in different places), group them by leaving no blank line
+between them.
- Version control systems are another way to keep track of changes in your
-program and keep a change log. @xref{Log Buffer}.
+ You should put a copyright notice and permission notice at the
+end of the change log file. Here is an example:
+
+@example
+Copyright 1997, 1998 Free Software Foundation, Inc.
+Copying and distribution of this file, with or without modification, are
+permitted provided the copyright notice and this notice are preserved.
+@end example
-@node Authors
-@section @file{AUTHORS} files
-@cindex @file{AUTHORS} file
-
- Programs which have many contributors usually include a file named
-@file{AUTHORS} in their distribution, which lists the individual
-contributions. Emacs has a special command for maintaining the
-@file{AUTHORS} file that is part of the Emacs distribution.
-
-@findex authors
- The @kbd{M-x authors} command prompts for the name of the root of the
-Emacs source directory. It then scans @file{ChangeLog} files and Lisp
-source files under that directory for information about authors of
-individual packages and people who made changes in source files, and
-puts the information it gleans into a buffer named @samp{*Authors*}.
-You can then edit the contents of that buffer and merge it with the
-existing @file{AUTHORS} file.
-
- Do not assume that this command finds all the contributors; don't
-assume that a person not listed in the output was not a contributor.
-If you merged in someone's contribution and did not put his name
-in the change log, he won't show up in @kbd{M-x authors} either.
+@noindent
+Of course, you should substitute the proper years and copyright holder.
@node Tags
@section Tags Tables
conventional name for a tags table file is @file{TAGS}.
Each entry in the tags table records the name of one tag, the name of the
-file that the tag is defined in (implicitly), and the position in that file
-of the tag's definition.
+file that the tag is defined in (implicitly), and the position in that
+file of the tag's definition. When a file parsed by @code{etags} is
+generated from a different source file, like a C file generated from a
+Cweb source file, the tags of the parsed file reference the source
+file.
Just what names from the described files are recorded in the tags table
depends on the programming language of the described file. They
You can tag function declarations and external variables in addition
to function definitions by giving the @samp{--declarations} option to
-@code{etags}.
+@code{etags}. You can tag struct members with the @samp{--members}
+option.
@item
In C++ code, in addition to all the tag constructs of C code, member
@item
In La@TeX{} text, the argument of any of the commands @code{\chapter},
@code{\section}, @code{\subsection}, @code{\subsubsection},
-@code{\eqno}, @code{\label}, @code{\ref}, @code{\cite}, @code{\bibitem},
-@code{\part}, @code{\appendix}, @code{\entry}, or @code{\index}, is a
-tag.@refill
+@code{\eqno}, @code{\label}, @code{\ref}, @code{\cite},
+@code{\bibitem}, @code{\part}, @code{\appendix}, @code{\entry},
+@code{\index}, @code{\def}, @code{\newcommand}, @code{\renewcommand},
+@code{\newenvironment} or @code{\renewenvironment} is a tag.@refill
Other commands can make tags as well, if you specify them in the
environment variable @env{TEXTAGS} before invoking @code{etags}. The
command names. For example,
@example
-TEXTAGS="def:newcommand:newenvironment"
+TEXTAGS="mycommand:myothercommand"
export TEXTAGS
@end example
@noindent
-specifies (using Bourne shell syntax) that the commands @samp{\def},
-@samp{\newcommand} and @samp{\newenvironment} also define tags.
+specifies (using Bourne shell syntax) that the commands
+@samp{\mycommand} and @samp{\myothercommand} also define tags.
@item
In Lisp code, any function defined with @code{defun}, any variable
defined with @code{defvar} or @code{defconst}, and in general the first
-argument of any expression that starts with @samp{(def} in column zero, is
+argument of any expression that starts with @samp{(def} in column zero is
a tag.
@item
@itemize @bullet
@item
-In Ada code, functions, procedures, packages, tasks, and types are
+In Ada code, functions, procedures, packages, tasks and types are
tags. Use the @samp{--packages-only} option to create tags for
packages only.
column 8 and followed by a period.
@item
-In Erlang code, the tags are the functions, records, and macros defined
+In Erlang code, the tags are the functions, records and macros defined
in the file.
@item
-In Fortran code, functions, subroutines and blockdata are tags.
+In Fortran code, functions, subroutines and block data are tags.
@item
-In makefiles, targets are tags.
+In HTML input files, the tags are the @code{title} and the @code{h1},
+@code{h2}, @code{h3} headers. Also, tags are @code{name=} in anchors
+and all occurrences of @code{id=}.
+
+@item
+In Lua input files, all functions are tags.
+
+@item
+In makefiles, targets are tags; additionally, variables are tags
+unless you specify @samp{--no-globals}.
@item
In Objective C code, tags include Objective C definitions for classes,
-class categories, methods, and protocols.
+class categories, methods and protocols. Tags for variables and
+functions in classes are named @samp{@var{class}::@var{variable}} and
+@samp{@var{class}::@var{function}}.
@item
In Pascal code, the tags are the functions and procedures defined in
the file.
@item
-In Perl code, the tags are the procedures defined by the @code{sub},
-@code{my} and @code{local} keywords. Use @samp{--globals} if you want
-to tag global variables.
+In Perl code, the tags are the packages, subroutines and variables
+defined by the @code{package}, @code{sub}, @code{my} and @code{local}
+keywords. Use @samp{--globals} if you want to tag global variables.
+Tags for subroutines are named @samp{@var{package}::@var{sub}}. The
+name for subroutines defined in the default package is
+@samp{main::@var{sub}}.
+
+@item
+In PHP code, tags are functions, classes and defines. When using the
+@samp{--members} option, vars are tags too.
@item
In PostScript code, the tags are the functions.
@item
-In Prolog code, a tag name appears at the left margin.
+In Prolog code, tags are predicates and rules at the beginning of
+line.
@item
In Python code, @code{def} or @code{class} at the beginning of a line
a tag, or records it for the wrong file, then Emacs cannot possibly
find its definition until you update the tags table. However, if the
position recorded in the tags table becomes a little bit wrong (due to
-other editing), the only consequence is a slight delay in finding the
+other editing), the worst consequence is a slight delay in finding the
tag. Even if the stored position is very far wrong, Emacs will still
-find the tag, after searching most of the file for it. Even that
-delay is hardly noticeable with today's computers.
+find the tag, after searching most of the file for it. That delay is
+hardly noticeable with today's computers.
- So you should update a tags table when you define new tags that you want
-to have listed, or when you move tag definitions from one file to another,
-or when changes become substantial. Normally there is no need to update
-the tags table after each edit, or even every day.
+ Thus, there is no need to update the tags table after each edit.
+You should update a tags table when you define new tags that you want
+to have listed, or when you move tag definitions from one file to
+another, or when changes become substantial.
One tags table can virtually include another. Specify the included
tags file name with the @samp{--include=@var{file}} option when
directory where the tags file was initially written. This way, you can
move an entire directory tree containing both the tags file and the
source files, and the tags file will still refer correctly to the source
-files.
+files. If the tags file is in @file{/dev}, however, the file names are
+made relative to the current working directory. This is useful, for
+example, when writing the tags to @file{/dev/stdout}.
If you specify absolute file names as arguments to @code{etags}, then
the tags file will contain absolute file names. This way, the tags file
entirely; then @code{etags} recognizes tags by regexp matching alone
(@pxref{Etags Regexps}).
- @samp{etags --help} prints the list of the languages @code{etags}
+ The option @samp{--parse-stdin=@var{file}} is mostly useful when
+calling @code{etags} from programs. It can be used (only once) in
+place of a file name on the command line. @code{Etags} will read from
+standard input and mark the produced tags as belonging to the file
+@var{file}.
+
+ @samp{etags --help} outputs the list of the languages @code{etags}
knows, and the file name rules for guessing the language. It also prints
a list of all the available @code{etags} options, together with a short
-explanation.
+explanation. If followed by one or more @samp{--language=@var{lang}}
+options, it outputs detailed information about how tags are generated for
+@var{lang}.
@node Etags Regexps
@subsection Etags Regexps
The @samp{--regex} option provides a general way of recognizing tags
-based on regexp matching. You can freely intermix it with file names.
-Each @samp{--regex} option adds to the preceding ones, and applies only
-to the following files. The syntax is:
+based on regexp matching. You can freely intermix this option with
+file names, and each one applies to the source files that follow it.
+If you specify multiple @samp{--regex} options, all of them are used
+in parallel. The syntax is:
@smallexample
---regex=/@var{tagregexp}[/@var{nameregexp}]/
+--regex=[@var{@{language@}}]/@var{tagregexp}/[@var{nameregexp}/]@var{modifiers}
@end smallexample
-@noindent
-where @var{tagregexp} is used to match the lines to tag. It is always
-anchored, that is, it behaves as if preceded by @samp{^}. If you want
-to account for indentation, just match any initial number of blanks by
-beginning your regular expression with @samp{[ \t]*}. In the regular
-expressions, @samp{\} quotes the next character, and @samp{\t} stands
-for the tab character. Note that @code{etags} does not handle the other
-C escape sequences for special characters.
-
-@cindex interval operator (in regexps)
- The syntax of regular expressions in @code{etags} is the same as in
-Emacs, augmented with the @dfn{interval operator}, which works as in
-@code{grep} and @code{ed}. The syntax of an interval operator is
-@samp{\@{@var{m},@var{n}\@}}, and its meaning is to match the preceding
-expression at least @var{m} times and up to @var{n} times.
-
- You should not match more characters with @var{tagregexp} than that
-needed to recognize what you want to tag. If the match is such that
-more characters than needed are unavoidably matched by @var{tagregexp}
-(as will usually be the case), you should add a @var{nameregexp}, to
-pick out just the tag. This will enable Emacs to find tags more
-accurately and to do completion on tag names more reliably. You can
-find some examples below.
-
- The option @samp{--ignore-case-regex} (or @samp{-c}) works like
-@samp{--regex}, except that matching ignores case. This is
-appropriate for certain programming languages.
-
- The @samp{-R} option deletes all the regexps defined with
-@samp{--regex} options. It applies to the file names following it, as
-you can see from the following example:
+ The essential part of the option value is @var{tagregexp}, the
+regexp for matching tags. It is always used anchored, that is, it
+only matches at the beginning of a line. If you want to allow
+indented tags, use a regexp that matches initial whitespace; start it
+with @samp{[ \t]*}.
+
+ In these regular expressions, @samp{\} quotes the next character, and
+all the GCC character escape sequences are supported (@samp{\a} for
+bell, @samp{\b} for back space, @samp{\d} for delete, @samp{\e} for
+escape, @samp{\f} for formfeed, @samp{\n} for newline, @samp{\r} for
+carriage return, @samp{\t} for tab, and @samp{\v} for vertical tab).
+
+ Ideally, @var{tagregexp} should not match more characters than are
+needed to recognize what you want to tag. If the syntax requires you
+to write @var{tagregexp} so it matches more characters beyond the tag
+itself, you should add a @var{nameregexp}, to pick out just the tag.
+This will enable Emacs to find tags more accurately and to do
+completion on tag names more reliably. You can find some examples
+below.
+
+ The @var{modifiers} are a sequence of zero or more characters that
+modify the way @code{etags} does the matching. A regexp with no
+modifiers is applied sequentially to each line of the input file, in a
+case-sensitive way. The modifiers and their meanings are:
+
+@table @samp
+@item i
+Ignore case when matching this regexp.
+@item m
+Match this regular expression against the whole file, so that
+multi-line matches are possible.
+@item s
+Match this regular expression against the whole file, and allow
+@samp{.} in @var{tagregexp} to match newlines.
+@end table
+
+ The @samp{-R} option cancels all the regexps defined by preceding
+@samp{--regex} options. It too applies to the file names following
+it. Here's an example:
@smallexample
-etags --regex=/@var{reg1}/ voo.doo --regex=/@var{reg2}/ \
+etags --regex=/@var{reg1}/i voo.doo --regex=/@var{reg2}/m \
bar.ber -R --lang=lisp los.er
@end smallexample
@file{bar.ber} according to their contents. @code{etags} also uses
@var{reg1} to recognize additional tags in @file{voo.doo}, and both
@var{reg1} and @var{reg2} to recognize additional tags in
-@file{bar.ber}. @code{etags} uses the Lisp tags rules, and no regexp
-matching, to recognize tags in @file{los.er}.
-
- You can specify a regular expression for a particular language, by
-writing @samp{@{lang@}} in front of it. Then @code{etags} will use
-the regular expression only for files of that language. (@samp{etags
---help} prints the list of languages recognised by @code{etags}.) The
+@file{bar.ber}. @var{reg1} is checked against each line of
+@file{voo.doo} and @file{bar.ber}, in a case-insensitive way, while
+@var{reg2} is checked against the whole @file{bar.ber} file,
+permitting multi-line matches, in a case-sensitive way. @code{etags}
+uses only the Lisp tags rules, with no user-specified regexp matching,
+to recognize tags in @file{los.er}.
+
+ You can restrict a @samp{--regex} option to match only files of a
+given language by using the optional prefix @var{@{language@}}.
+(@samp{etags --help} prints the list of languages recognized by
+@code{etags}.) This is particularly useful when storing many
+predefined regular expressions for @code{etags} in a file. The
following example tags the @code{DEFVAR} macros in the Emacs source
files, for the C language only:
@end smallexample
@noindent
-This feature is particularly useful when you store a list of regular
-expressions in a file. The following option syntax instructs
-@code{etags} to read two files of regular expressions. The regular
-expressions contained in the second file are matched without regard to
-case.
+When you have complex regular expressions, you can store the list of
+them in a file. The following option syntax instructs @code{etags} to
+read two files of regular expressions. The regular expressions
+contained in the second file are matched without regard to case.
@smallexample
---regex=@@first-file --ignore-case-regex=@@second-file
+--regex=@@@var{case-sensitive-file} --ignore-case-regex=@@@var{ignore-case-file}
@end smallexample
@noindent
-A regex file contains one regular expressions per line. Empty lines,
-and lines beginning with space or tab are ignored. When the first
-character in a line is @samp{@@}, @code{etags} assumes that the rest
-of the line is the name of a file of regular expressions; thus, one
-such file can include another file. All the other lines are taken to
-be regular expressions. If the first non-whitespace text on the line
-is @samp{--}, that line is a comment.
-
- For example, one can create a file called @samp{emacs.tags} with the
+A regex file for @code{etags} contains one regular expression per
+line. Empty lines, and lines beginning with space or tab are ignored.
+When the first character in a line is @samp{@@}, @code{etags} assumes
+that the rest of the line is the name of another file of regular
+expressions; thus, one such file can include another file. All the
+other lines are taken to be regular expressions. If the first
+non-whitespace text on the line is @samp{--}, that line is a comment.
+
+ For example, we can create a file called @samp{emacs.tags} with the
following contents:
@smallexample
@vindex tags-file-name
@findex visit-tags-table
- Emacs has at any time one @dfn{selected} tags table, and all the commands
-for working with tags tables use the selected one. To select a tags table,
-type @kbd{M-x visit-tags-table}, which reads the tags table file name as an
-argument. The name @file{TAGS} in the default directory is used as the
-default file name.
-
- All this command does is store the file name in the variable
-@code{tags-file-name}. Emacs does not actually read in the tags table
-contents until you try to use them. Setting this variable yourself is just
-as good as using @code{visit-tags-table}. The variable's initial value is
-@code{nil}; that value tells all the commands for working with tags tables
-that they must ask for a tags table file name to use.
+ Emacs has at any time one @dfn{selected} tags table, and all the
+commands for working with tags tables use the selected one. To select
+a tags table, type @kbd{M-x visit-tags-table}, which reads the tags
+table file name as an argument, with @file{TAGS} in the default
+directory as the default.
+
+ Emacs does not actually read in the tags table contents until you
+try to use them; all @code{visit-tags-table} does is store the file
+name in the variable @code{tags-file-name}, and setting the variable
+yourself is just as good. The variable's initial value is @code{nil};
+that value tells all the commands for working with tags tables that
+they must ask for a tags table file name to use.
Using @code{visit-tags-table} when a tags table is already loaded
gives you a choice: you can add the new tags table to the current list
of tags tables, or start a new list. The tags commands use all the tags
tables in the current list. If you start a new list, the new tags table
is used @emph{instead} of others. If you add the new table to the
-current list, it is used @emph{as well as} the others. When the tags
-commands scan the list of tags tables, they don't always start at the
-beginning of the list; they start with the first tags table (if any)
-that describes the current file, proceed from there to the end of the
-list, and then scan from the beginning of the list until they have
-covered all the tables in the list.
+current list, it is used @emph{as well as} the others.
@vindex tags-table-list
You can specify a precise list of tags tables by setting the variable
@findex find-tag-other-frame
Like most commands that can switch buffers, @code{find-tag} has a
variant that displays the new buffer in another window, and one that
-makes a new frame for it. The former is @kbd{C-x 4 .}, which invokes
-the command @code{find-tag-other-window}. The latter is @kbd{C-x 5 .},
+makes a new frame for it. The former is @w{@kbd{C-x 4 .}}, which invokes
+the command @code{find-tag-other-window}. The latter is @w{@kbd{C-x 5 .}},
which invokes @code{find-tag-other-frame}.
To move back to places you've found tags recently, use @kbd{C-u -
M-.}; more generally, @kbd{M-.} with a negative numeric argument. This
-command can take you to another buffer. @kbd{C-x 4 .} with a negative
+command can take you to another buffer. @w{@kbd{C-x 4 .}} with a negative
argument finds the previous tag location in another window.
@kindex M-*
@cindex search and replace in multiple files
@cindex multiple-file search and replace
- The commands in this section visit and search all the files listed in the
-selected tags table, one by one. For these commands, the tags table serves
-only to specify a sequence of files to search.
+ The commands in this section visit and search all the files listed
+in the selected tags table, one by one. For these commands, the tags
+table serves only to specify a sequence of files to search. These
+commands scan the list of tags tables starting with the first tags
+table (if any) that describes the current file, proceed from there to
+the end of the list, and then scan from the beginning of the list
+until they have covered all the tables in the list.
@table @kbd
@item M-x tags-search @key{RET} @var{regexp} @key{RET}
It may have struck you that @code{tags-search} is a lot like
@code{grep}. You can also run @code{grep} itself as an inferior of
-Emacs and have Emacs show you the matching lines one by one. This works
-much like running a compilation; finding the source locations of the
-@code{grep} matches works like finding the compilation errors.
-@xref{Compilation}.
+Emacs and have Emacs show you the matching lines one by one.
+@xref{Grep Searching}.
@node List Tags
@subsection Tags Table Inquiries
@vindex tags-tag-face
@vindex tags-apropos-additional-actions
-You can customize the appearance of the output with the face
-@code{tags-tag-face}. You can display additional output with @kbd{M-x
-tags-apropos} by customizing the variable
+ You can customize the appearance of the output by setting the
+variable @code{tags-tag-face} to a face. You can display additional
+output with @kbd{M-x tags-apropos} by customizing the variable
@code{tags-apropos-additional-actions}---see its documentation for
details.
You can also use the collection of tag names to complete a symbol
name in the buffer. @xref{Symbol Completion}.
-@node Emerge
-@section Merging Files with Emerge
-@cindex Emerge
-@cindex merging files
-
-It's not unusual for programmers to get their signals crossed and modify
-the same program in two different directions. To recover from this
-confusion, you need to merge the two versions. Emerge makes this
-easier. See also @ref{Comparing Files}, for commands to compare
-in a more manual fashion, and @ref{,Ediff,, ediff, The Ediff Manual}.
-
-@menu
-* Overview of Emerge:: How to start Emerge. Basic concepts.
-* Submodes of Emerge:: Fast mode vs. Edit mode.
- Skip Prefers mode and Auto Advance mode.
-* State of Difference:: You do the merge by specifying state A or B
- for each difference.
-* Merge Commands:: Commands for selecting a difference,
- changing states of differences, etc.
-* Exiting Emerge:: What to do when you've finished the merge.
-* Combining in Emerge:: How to keep both alternatives for a difference.
-* Fine Points of Emerge:: Misc.
-@end menu
-
-@node Overview of Emerge
-@subsection Overview of Emerge
-
-To start Emerge, run one of these four commands:
-
-@table @kbd
-@item M-x emerge-files
-@findex emerge-files
-Merge two specified files.
-
-@item M-x emerge-files-with-ancestor
-@findex emerge-files-with-ancestor
-Merge two specified files, with reference to a common ancestor.
-
-@item M-x emerge-buffers
-@findex emerge-buffers
-Merge two buffers.
-
-@item M-x emerge-buffers-with-ancestor
-@findex emerge-buffers-with-ancestor
-Merge two buffers with reference to a common ancestor in a third
-buffer.
-@end table
-
-@cindex merge buffer (Emerge)
-@cindex A and B buffers (Emerge)
- The Emerge commands compare two files or buffers, and display the
-comparison in three buffers: one for each input text (the @dfn{A buffer}
-and the @dfn{B buffer}), and one (the @dfn{merge buffer}) where merging
-takes place. The merge buffer shows the full merged text, not just the
-differences. Wherever the two input texts differ, you can choose which
-one of them to include in the merge buffer.
-
- The Emerge commands that take input from existing buffers use only the
-accessible portions of those buffers, if they are narrowed
-(@pxref{Narrowing}).
-
- If a common ancestor version is available, from which the two texts to
-be merged were both derived, Emerge can use it to guess which
-alternative is right. Wherever one current version agrees with the
-ancestor, Emerge presumes that the other current version is a deliberate
-change which should be kept in the merged version. Use the
-@samp{with-ancestor} commands if you want to specify a common ancestor
-text. These commands read three file or buffer names---variant A,
-variant B, and the common ancestor.
-
- After the comparison is done and the buffers are prepared, the
-interactive merging starts. You control the merging by typing special
-@dfn{merge commands} in the merge buffer. The merge buffer shows you a
-full merged text, not just differences. For each run of differences
-between the input texts, you can choose which one of them to keep, or
-edit them both together.
-
- The merge buffer uses a special major mode, Emerge mode, with commands
-for making these choices. But you can also edit the buffer with
-ordinary Emacs commands.
-
- At any given time, the attention of Emerge is focused on one
-particular difference, called the @dfn{selected} difference. This
-difference is marked off in the three buffers like this:
-
-@example
-vvvvvvvvvvvvvvvvvvvv
-@var{text that differs}
-^^^^^^^^^^^^^^^^^^^^
-@end example
-
-@noindent
-Emerge numbers all the differences sequentially and the mode
-line always shows the number of the selected difference.
-
- Normally, the merge buffer starts out with the A version of the text.
-But when the A version of a difference agrees with the common ancestor,
-then the B version is initially preferred for that difference.
-
- Emerge leaves the merged text in the merge buffer when you exit. At
-that point, you can save it in a file with @kbd{C-x C-w}. If you give a
-numeric argument to @code{emerge-files} or
-@code{emerge-files-with-ancestor}, it reads the name of the output file
-using the minibuffer. (This is the last file name those commands read.)
-Then exiting from Emerge saves the merged text in the output file.
-
- Normally, Emerge commands save the output buffer in its file when you
-exit. If you abort Emerge with @kbd{C-]}, the Emerge command does not
-save the output buffer, but you can save it yourself if you wish.
-
-@node Submodes of Emerge
-@subsection Submodes of Emerge
-
- You can choose between two modes for giving merge commands: Fast mode
-and Edit mode. In Fast mode, basic merge commands are single
-characters, but ordinary Emacs commands are disabled. This is
-convenient if you use only merge commands. In Edit mode, all merge
-commands start with the prefix key @kbd{C-c C-c}, and the normal Emacs
-commands are also available. This allows editing the merge buffer, but
-slows down Emerge operations.
-
- Use @kbd{e} to switch to Edit mode, and @kbd{C-c C-c f} to switch to
-Fast mode. The mode line indicates Edit and Fast modes with @samp{E}
-and @samp{F}.
-
- Emerge has two additional submodes that affect how particular merge
-commands work: Auto Advance mode and Skip Prefers mode.
-
- If Auto Advance mode is in effect, the @kbd{a} and @kbd{b} commands
-advance to the next difference. This lets you go through the merge
-faster as long as you simply choose one of the alternatives from the
-input. The mode line indicates Auto Advance mode with @samp{A}.
-
- If Skip Prefers mode is in effect, the @kbd{n} and @kbd{p} commands
-skip over differences in states prefer-A and prefer-B (@pxref{State of
-Difference}). Thus you see only differences for which neither version
-is presumed ``correct.'' The mode line indicates Skip Prefers mode with
-@samp{S}.
-
-@findex emerge-auto-advance-mode
-@findex emerge-skip-prefers-mode
- Use the command @kbd{s a} (@code{emerge-auto-advance-mode}) to set or
-clear Auto Advance mode. Use @kbd{s s}
-(@code{emerge-skip-prefers-mode}) to set or clear Skip Prefers mode.
-These commands turn on the mode with a positive argument, turns it off
-with a negative or zero argument, and toggle the mode with no argument.
-
-@node State of Difference
-@subsection State of a Difference
-
- In the merge buffer, a difference is marked with lines of @samp{v} and
-@samp{^} characters. Each difference has one of these seven states:
-
-@table @asis
-@item A
-The difference is showing the A version. The @kbd{a} command always
-produces this state; the mode line indicates it with @samp{A}.
-
-@item B
-The difference is showing the B version. The @kbd{b} command always
-produces this state; the mode line indicates it with @samp{B}.
-
-@item default-A
-@itemx default-B
-The difference is showing the A or the B state by default, because you
-haven't made a choice. All differences start in the default-A state
-(and thus the merge buffer is a copy of the A buffer), except those for
-which one alternative is ``preferred'' (see below).
-
-When you select a difference, its state changes from default-A or
-default-B to plain A or B. Thus, the selected difference never has
-state default-A or default-B, and these states are never displayed in
-the mode line.
-
-The command @kbd{d a} chooses default-A as the default state, and @kbd{d
-b} chooses default-B. This chosen default applies to all differences
-which you haven't ever selected and for which no alternative is preferred.
-If you are moving through the merge sequentially, the differences you
-haven't selected are those following the selected one. Thus, while
-moving sequentially, you can effectively make the A version the default
-for some sections of the merge buffer and the B version the default for
-others by using @kbd{d a} and @kbd{d b} between sections.
-
-@item prefer-A
-@itemx prefer-B
-The difference is showing the A or B state because it is
-@dfn{preferred}. This means that you haven't made an explicit choice,
-but one alternative seems likely to be right because the other
-alternative agrees with the common ancestor. Thus, where the A buffer
-agrees with the common ancestor, the B version is preferred, because
-chances are it is the one that was actually changed.
-
-These two states are displayed in the mode line as @samp{A*} and @samp{B*}.
-
-@item combined
-The difference is showing a combination of the A and B states, as a
-result of the @kbd{x c} or @kbd{x C} commands.
-
-Once a difference is in this state, the @kbd{a} and @kbd{b} commands
-don't do anything to it unless you give them a numeric argument.
-
-The mode line displays this state as @samp{comb}.
-@end table
-
-@node Merge Commands
-@subsection Merge Commands
-
- Here are the Merge commands for Fast mode; in Edit mode, precede them
-with @kbd{C-c C-c}:
-
-@table @kbd
-@item p
-Select the previous difference.
-
-@item n
-Select the next difference.
-
-@item a
-Choose the A version of this difference.
-
-@item b
-Choose the B version of this difference.
-
-@item C-u @var{n} j
-Select difference number @var{n}.
-
-@item .
-Select the difference containing point. You can use this command in the
-merge buffer or in the A or B buffer.
-
-@item q
-Quit---finish the merge.
-
-@item C-]
-Abort---exit merging and do not save the output.
-
-@item f
-Go into Fast mode. (In Edit mode, this is actually @kbd{C-c C-c f}.)
-
-@item e
-Go into Edit mode.
-
-@item l
-Recenter (like @kbd{C-l}) all three windows.
-
-@item -
-Specify part of a prefix numeric argument.
-
-@item @var{digit}
-Also specify part of a prefix numeric argument.
-
-@item d a
-Choose the A version as the default from here down in
-the merge buffer.
-
-@item d b
-Choose the B version as the default from here down in
-the merge buffer.
-
-@item c a
-Copy the A version of this difference into the kill ring.
-
-@item c b
-Copy the B version of this difference into the kill ring.
-
-@item i a
-Insert the A version of this difference at point.
-
-@item i b
-Insert the B version of this difference at point.
-
-@item m
-Put point and mark around the difference.
-
-@item ^
-Scroll all three windows down (like @kbd{M-v}).
-
-@item v
-Scroll all three windows up (like @kbd{C-v}).
-
-@item <
-Scroll all three windows left (like @kbd{C-x <}).
-
-@item >
-Scroll all three windows right (like @kbd{C-x >}).
-
-@item |
-Reset horizontal scroll on all three windows.
-
-@item x 1
-Shrink the merge window to one line. (Use @kbd{C-u l} to restore it
-to full size.)
-
-@item x c
-Combine the two versions of this difference (@pxref{Combining in
-Emerge}).
-
-@item x f
-Show the names of the files/buffers Emerge is operating on, in a Help
-window. (Use @kbd{C-u l} to restore windows.)
-
-@item x j
-Join this difference with the following one.
-(@kbd{C-u x j} joins this difference with the previous one.)
-
-@item x s
-Split this difference into two differences. Before you use this
-command, position point in each of the three buffers at the place where
-you want to split the difference.
-
-@item x t
-Trim identical lines off the top and bottom of the difference.
-Such lines occur when the A and B versions are
-identical but differ from the ancestor version.
-@end table
-
-@node Exiting Emerge
-@subsection Exiting Emerge
-
- The @kbd{q} command (@code{emerge-quit}) finishes the merge, storing
-the results into the output file if you specified one. It restores the
-A and B buffers to their proper contents, or kills them if they were
-created by Emerge and you haven't changed them. It also disables the
-Emerge commands in the merge buffer, since executing them later could
-damage the contents of the various buffers.
-
- @kbd{C-]} aborts the merge. This means exiting without writing the
-output file. If you didn't specify an output file, then there is no
-real difference between aborting and finishing the merge.
-
- If the Emerge command was called from another Lisp program, then its
-return value is @code{t} for successful completion, or @code{nil} if you
-abort.
-
-@node Combining in Emerge
-@subsection Combining the Two Versions
-
- Sometimes you want to keep @emph{both} alternatives for a particular
-difference. To do this, use @kbd{x c}, which edits the merge buffer
-like this:
-
-@example
-@group
-#ifdef NEW
-@var{version from A buffer}
-#else /* not NEW */
-@var{version from B buffer}
-#endif /* not NEW */
-@end group
-@end example
-
-@noindent
-@vindex emerge-combine-versions-template
-While this example shows C preprocessor conditionals delimiting the two
-alternative versions, you can specify the strings to use by setting
-the variable @code{emerge-combine-versions-template} to a string of your
-choice. In the string, @samp{%a} says where to put version A, and
-@samp{%b} says where to put version B. The default setting, which
-produces the results shown above, looks like this:
-
-@example
-@group
-"#ifdef NEW\n%a#else /* not NEW */\n%b#endif /* not NEW */\n"
-@end group
-@end example
-
-@node Fine Points of Emerge
-@subsection Fine Points of Emerge
-
- During the merge, you mustn't try to edit the A and B buffers yourself.
-Emerge modifies them temporarily, but ultimately puts them back the way
-they were.
-
- You can have any number of merges going at once---just don't use any one
-buffer as input to more than one merge at once, since the temporary
-changes made in these buffers would get in each other's way.
-
- Starting Emerge can take a long time because it needs to compare the
-files fully. Emacs can't do anything else until @code{diff} finishes.
-Perhaps in the future someone will change Emerge to do the comparison in
-the background when the input files are large---then you could keep on
-doing other things with Emacs until Emerge is ready to accept
-commands.
-
-@vindex emerge-startup-hook
- After setting up the merge, Emerge runs the hook
-@code{emerge-startup-hook} (@pxref{Hooks}).
+@ifnottex
+@include emerge-xtra.texi
+@end ifnottex
+@ignore
+ arch-tag: b9d83dfb-82ea-4ff6-bab5-05a3617091fb
+@end ignore