@xref{Interlocking,, Simultaneous Editing}.
@vindex require-final-newline
- If the value of the variable @code{require-final-newline} is @code{t},
-Emacs silently puts a newline at the end of any file that doesn't
-already end in one, every time a file is saved or written. If the value
-is @code{nil}, Emacs leaves the end of the file unchanged; if it's
-neither @code{nil} nor @code{t}, Emacs asks you whether to add a
-newline. The default is @code{nil}.
+ If the value of the variable @code{require-final-newline} is
+@code{t}, Emacs silently puts a newline at the end of any file that
+doesn't already end in one, every time a file is saved or written. If
+the value is @code{visit}, Emacs adds a newline at the end of any file
+that doesn't have one, just after it visits the file. (This marks the
+buffer as modified, and you can undo it.) If the value is
+@code{visit-save}, that means to add newlines both on visiting and on
+saving. If the value is @code{nil}, Emacs leaves the end of the file
+unchanged; if it's neither @code{nil} nor @code{t}, Emacs asks you
+whether to add a newline. The default is @code{nil}.
+
+@vindex mode-require-final-newline
+ Many major modes are designed for specific kinds of files that are
+always supposed to end in newlines. These major modes set the
+variable @code{require-final-newline} according to
+@code{mode-require-final-newline}. By setting the latter variable,
+you can control how these modes handle final newlines.
@menu
* Backup:: How Emacs saves the old version of your file.
description of what was changed in that version.
The Emacs version control interface is called VC. Its commands work
-with three version control systems---RCS, CVS, and SCCS. The GNU
-project recommends RCS and CVS, which are free software and available
-from the Free Software Foundation. We also have free software to
-replace SCCS, known as CSSC; if you are using SCCS and don't want to
-make the incompatible change to RCS or CVS, you can switch to CSSC.
+with different version control systems---currently, it supports CVS,
+GNU Arch, RCS, Meta-CVS, Subversion, and SCCS. Of these, the GNU
+project distributes CVS, GNU Arch, and RCS; we recommend that you use
+either CVS or GNU Arch for your projects, and RCS for individual
+files. We also have free software to replace SCCS, known as CSSC; if
+you are using SCCS and don't want to make the incompatible change to
+RCS or CVS, you can switch to CSSC.
VC is enabled by default in Emacs. To disable it, set the
customizable variable @code{vc-handled-backends} to @code{nil}
@node Version Systems
@subsubsection Supported Version Control Systems
-@cindex RCS
@cindex back end (version control)
- VC currently works with three different version control systems or
-``back ends'': RCS, CVS, and SCCS.
-
- RCS is a free version control system that is available from the Free
-Software Foundation. It is perhaps the most mature of the supported
-back ends, and the VC commands are conceptually closest to RCS. Almost
-everything you can do with RCS can be done through VC.
+ VC currently works with six different version control systems or
+``back ends'': CVS, GNU Arch, RCS, Meta-CVS, Subversion, and SCCS.
@cindex CVS
- CVS is built on top of RCS, and extends the features of RCS, allowing
-for more sophisticated release management, and concurrent multi-user
-development. VC supports basic editing operations under CVS, but for
-some less common tasks you still need to call CVS from the command line.
-Note also that before using CVS you must set up a repository, which is a
-subject too complex to treat here.
+ CVS is a free version control system that is used for the majority
+of free software projects today. It allows concurrent multi-user
+development either locally or over the network. Some of its
+shortcomings, corrected by newer systems such as GNU Arch, are that it
+lacks atomic commits or support for renaming files. VC supports all
+basic editing operations under CVS, but for some less common tasks you
+still need to call CVS from the command line. Note also that before
+using CVS you must set up a repository, which is a subject too complex
+to treat here.
+
+@cindex GNU Arch
+@cindex Arch
+ GNU Arch is a new version control system that is designed for
+distributed work. It differs in many ways from old well-known
+systems, such as CVS and RCS. It supports different transports for
+interoperating between users, offline operations, and it has good
+branching and merging features. It also supports atomic commits, and
+history of file renaming and moving. VC does not support all
+operations provided by GNU Arch, so you must sometimes invoke it from
+the command line, or use a specialized module.
+
+@cindex RCS
+ RCS is the free version control system around which VC was initially
+built. The VC commands are therefore conceptually closest to RCS.
+Almost everything you can do with RCS can be done through VC. You
+cannot use RCS over the network though, and it only works at the level
+of individual files, rather than projects. You should use it if you
+want a simple, yet reliable tool for handling individual files.
+
+@cindex SVN
+@cindex Subversion
+ Subversion is a free version control system designed to be similar
+to CVS but without CVS's problems. Subversion supports atomic commits,
+and versions directories, symbolic links, meta-data, renames, copies,
+and deletes. It can be used via http or via its own protocol.
+
+@cindex MCVS
+@cindex Meta-CVS
+ Meta-CVS is another attempt to solve problems, arising in CVS. It
+supports directory structure versioning, improved branching and
+merging, and use of symbolic links and meta-data in repositories.
@cindex SCCS
SCCS is a proprietary but widely used version control system. In
-terms of capabilities, it is the weakest of the three that VC
-supports. VC compensates for certain features missing in SCCS
-(snapshots, for example) by implementing them itself, but some other VC
-features, such as multiple branches, are not available with SCCS. You
-should use SCCS only if for some reason you cannot use RCS.
+terms of capabilities, it is the weakest of the six that VC supports.
+VC compensates for certain features missing in SCCS (snapshots, for
+example) by implementing them itself, but some other VC features, such
+as multiple branches, are not available with SCCS. You should use
+SCCS only if for some reason you cannot use RCS, or one of the
+higher-level systems such as CVS or GNU Arch.
@node VC Concepts
@subsubsection Concepts of Version Control
Compare the specified two versions of @var{file}.
@item C-x v g
-Display the result of the CVS annotate command using colors.
+Display the file with per-line version information and using colors.
@end table
@findex vc-version-other-window
@findex vc-annotate
@kindex C-x v g
- For CVS-controlled files, you can display the result of the CVS
-annotate command, using colors to enhance the visual appearance. Use
-the command @kbd{M-x vc-annotate} to do this. It creates a new buffer
+ For some backends, you can display the file @dfn{annotated} with
+per-line version information and using colors to enhance the visual
+appearance, with the the command @kbd{M-x vc-annotate}.
+It creates a new buffer
to display file's text, colored to show how old each part is. Text
colored red is new, blue means old, and intermediate colors indicate
intermediate ages. By default, the time scale is 360 days, so that
for moving around in the file, but none for changing it; type @kbd{?}
while viewing for a list of them. They are mostly the same as normal
Emacs cursor motion commands. To exit from viewing, type @kbd{q}.
-The commands for viewing are defined by a special major mode called View
+The commands for viewing are defined by a special minor mode called View
mode.
A related command, @kbd{M-x view-buffer}, views a buffer already present