maintaining.texi 99.3 KB
Newer Older
1
@c This is part of the Emacs manual., Abbrevs, This is part of the Emacs manual., Top
Paul Eggert's avatar
Paul Eggert committed
2
@c Copyright (C) 1985-1987, 1993-1995, 1997, 1999-2015 Free Software
3
@c Foundation, Inc.
Glenn Morris's avatar
Glenn Morris committed
4
@c See file emacs.texi for copying conditions.
5
@node Maintaining
Glenn Morris's avatar
Glenn Morris committed
6 7 8
@chapter Maintaining Large Programs

  This chapter describes Emacs features for maintaining large
Glenn Morris's avatar
Glenn Morris committed
9 10
programs.  If you are maintaining a large Lisp program, then in
addition to the features described here, you may find
Paul Eggert's avatar
Paul Eggert committed
11
the Emacs Lisp Regression Testing (ERT) library useful
Glenn Morris's avatar
Glenn Morris committed
12
(@pxref{Top,,ERT,ert, Emacs Lisp Regression Testing}).
Glenn Morris's avatar
Glenn Morris committed
13 14

@menu
15
* Version Control::     Using version control systems.
16 17 18
* Change Log::          Maintaining a change history for your program.
* Tags::                Go directly to any function in your program in one
                          command.  Tags remembers which file it is in.
19
* EDE::                 An integrated development environment for Emacs.
Glenn Morris's avatar
Glenn Morris committed
20 21 22 23 24
@ifnottex
* Emerge::              A convenient way of merging two versions of a program.
@end ifnottex
@end menu

25 26 27 28
@node Version Control
@section Version Control
@cindex version control

29
  A @dfn{version control system} is a program that can record multiple
30
versions of a source file, storing information such as the creation
31 32 33
time of each version, who made it, and a description of what was
changed.

34 35 36
  The Emacs version control interface is called @dfn{VC}@.  VC
commands work with several different version control systems;
currently, it supports Bazaar, CVS, Git, Mercurial, Monotone, RCS,
37
SCCS/CSSC, and Subversion.  Of these, the GNU project distributes CVS,
38
RCS, and Bazaar.
39 40 41 42

  VC is enabled automatically whenever you visit a file governed by a
version control system.  To disable VC entirely, set the customizable
variable @code{vc-handled-backends} to @code{nil}
43 44 45 46 47 48 49
@iftex
(@pxref{Customizing VC,,,emacs-xtra, Specialized Emacs Features}).
@end iftex
@ifnottex
(@pxref{Customizing VC}).
@end ifnottex

Eli Zaretskii's avatar
Eli Zaretskii committed
50 51 52 53 54 55 56 57 58 59 60
@findex vc-refresh-state
@findex vc-state-refresh
  To update the VC state information for the file visited in the
current buffer, use the command @code{vc-refresh-state}.  This command
is useful when you perform version control commands outside Emacs
(e.g., from the shell prompt), or if you put the buffer's file under a
different version control system, or remove it from version control
entirely.  A companion command @code{vc-state-refresh} does the same,
but does not consider switching the version control system or removal
from VC.

61 62 63 64
@menu
* Introduction to VC::  How version control works in general.
* VC Mode Line::        How the mode line shows version control status.
* Basic VC Editing::    How to edit a file under version control.
65
* Log Buffer::          Features available in log entry buffers.
66
* Registering::         Putting a file under version control.
67
* Old Revisions::       Examining and comparing old versions.
68 69
* VC Change Log::       Viewing the VC Change Log.
* VC Undo::             Canceling changes before or after committing.
70
* VC Ignore::           Ignore files under version control system.
71 72 73 74 75 76 77 78 79 80 81 82
* VC Directory Mode::   Listing files managed by version control.
* Branches::            Multiple lines of development.
@ifnottex
* Miscellaneous VC::    Various other commands and features of VC.
* Customizing VC::      Variables that change VC's behavior.
@end ifnottex
@end menu

@node Introduction to VC
@subsection Introduction to Version Control

  VC allows you to use a version control system from within Emacs,
83 84 85 86 87
integrating the version control operations smoothly with editing.  It
provides a uniform interface for common operations in many version
control operations.

  Some uncommon or intricate version control operations, such as
88 89
altering repository settings, are not supported in VC@.  You should
perform such tasks outside Emacs, e.g., via the command line.
90 91 92 93 94 95 96

  This section provides a general overview of version control, and
describes the version control systems that VC supports.  You can skip
this section if you are already familiar with the version control system
you want to use.

@menu
97
* Why Version Control?::    Understanding the problems it addresses.
98 99
* Version Control Systems:: Supported version control back-end systems.
* VCS Concepts::            Words and concepts related to version control.
100 101 102
* VCS Merging::             How file conflicts are handled.
* VCS Changesets::          How changes are grouped.
* VCS Repositories::        Where version control repositories are stored.
103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133
* Types of Log File::       The VCS log in contrast to the ChangeLog.
@end menu

@node Why Version Control?
@subsubsection Understanding the problems it addresses

  Version control systems provide you with three important
capabilities:

@itemize @bullet
@item
@dfn{Reversibility}: the ability to back up to a previous state if you
discover that some modification you did was a mistake or a bad idea.

@item
@dfn{Concurrency}: the ability to have many people modifying the same
collection of files knowing that conflicting modifications can be
detected and resolved.

@item
@dfn{History}: the ability to attach historical data to your data,
such as explanatory comments about the intention behind each change to
it.  Even for a programmer working solo, change histories are an
important aid to memory; for a multi-person project, they are a
vitally important form of communication among developers.
@end itemize

@node Version Control Systems
@subsubsection Supported Version Control Systems

@cindex back end (version control)
134 135
  VC currently works with many different version control systems,
which it refers to as @dfn{back ends}:
136 137 138 139 140 141 142

@itemize @bullet

@cindex SCCS
@item
SCCS was the first version control system ever built, and was long ago
superseded by more advanced ones.  VC compensates for certain features
143
missing in SCCS (e.g., tag names for releases) by implementing them
144 145 146 147 148
itself.  Other VC features, such as multiple branches, are simply
unavailable.  Since SCCS is non-free, we recommend avoiding it.

@cindex CSSC
@item
149
CSSC is a free replacement for SCCS@.  You should use CSSC only if, for
150 151 152 153 154 155
some reason, you cannot use a more recent and better-designed version
control system.

@cindex RCS
@item
RCS is the free version control system around which VC was initially
156 157 158
built.  It is relatively primitive: it cannot be used over the
network, and works at the level of individual files.  Almost
everything you can do with RCS can be done through VC.
159 160 161 162 163 164

@cindex CVS
@item
CVS is the free version control system that was, until recently (circa
2008), used by the majority of free software projects.  Nowadays, it
is slowly being superseded by newer systems.  CVS allows concurrent
165 166 167
multi-user development either locally or over the network.  Unlike
newer systems, it lacks support for atomic commits and file
moving/renaming.  VC supports all basic editing operations under CVS.
168 169 170 171

@cindex SVN
@cindex Subversion
@item
172
Subversion (svn) is a free version control system designed to be
173 174 175
similar to CVS but without its problems (e.g., it supports atomic
commits of filesets, and versioning of directories, symbolic links,
meta-data, renames, copies, and deletes).
176 177 178

@cindex git
@item
179
Git is a decentralized version control system originally invented by
180
Linus Torvalds to support development of Linux (his kernel).  VC
181
supports many common Git operations, but others, such as repository
182
syncing, must be done from the command line.
183 184 185 186

@cindex hg
@cindex Mercurial
@item
187
Mercurial (hg) is a decentralized version control system broadly
188
resembling Git.  VC supports most Mercurial commands, with the
189
exception of repository sync operations.
190 191 192 193

@cindex bzr
@cindex Bazaar
@item
194 195
Bazaar (bzr) is a decentralized version control system that supports
both repository-based and decentralized versioning.  VC supports most
196
basic editing operations under Bazaar.
197

Eric S. Raymond's avatar
Eric S. Raymond committed
198 199 200 201
@cindex SRC
@cindex src
@item
SRC (src) is RCS, reloaded - a specialized version-control system
202
designed for single-file projects worked on by only one person.  It
Eric S. Raymond's avatar
Eric S. Raymond committed
203
allows multiple files with independent version-control histories to
204
exist in one directory, and is thus particularly well suited for
Eric S. Raymond's avatar
Eric S. Raymond committed
205 206 207 208
maintaining small documents, scripts, and dotfiles.  While it uses RCS
for revision storage, it presents a modern user interface featuring
lockless operation and integer sequential version numbers.  VC
supports almost all SRC operations.
209
@end itemize
Eric S. Raymond's avatar
Eric S. Raymond committed
210

211 212 213 214 215 216 217 218 219 220 221 222 223 224
@node VCS Concepts
@subsubsection Concepts of Version Control

@cindex repository
@cindex registered file
   When a file is under version control, we say that it is
@dfn{registered} in the version control system.  The system has a
@dfn{repository} which stores both the file's present state and its
change history---enough to reconstruct the current version or any
earlier version.  The repository also contains other information, such
as @dfn{log entries} that describe the changes made to each file.

@cindex work file
@cindex checking out files
225 226 227
  The copy of a version-controlled file that you actually edit is
called the @dfn{work file}.  You can change each work file as you
would an ordinary file.  After you are done with a set of changes, you
228 229
may @dfn{commit} (or @dfn{check in}) the changes; this records the
changes in the repository, along with a descriptive log entry.
230

231 232 233
@cindex working tree
  A directory tree of work files is called a @dfn{working tree}.

234 235
@cindex revision
@cindex revision ID
236 237 238 239 240
  Each commit creates a new @dfn{revision} in the repository.  The
version control system keeps track of all past revisions and the
changes that were made in each revision.  Each revision is named by a
@dfn{revision ID}, whose format depends on the version control system;
in the simplest case, it is just an integer.
241 242

  To go beyond these basic concepts, you will need to understand three
243 244 245 246
aspects in which version control systems differ.  As explained in the
next three sections, they can be lock-based or merge-based; file-based
or changeset-based; and centralized or decentralized.  VC handles all
these modes of operation, but it cannot hide the differences.
247

248 249 250
@node VCS Merging
@subsubsection Merge-based vs lock-based Version Control

251 252 253 254
  A version control system typically has some mechanism to coordinate
between users who want to change the same file.  There are two ways to
do this: merging and locking.

255
@cindex merging-based version
256 257 258 259
  In a version control system that uses merging, each user may modify
a work file at any time.  The system lets you @dfn{merge} your work
file, which may contain changes that have not been committed, with the
latest changes that others have committed.
260

261
@cindex locking-based version
262 263 264 265 266 267
  Older version control systems use a @dfn{locking} scheme instead.
Here, work files are normally read-only.  To edit a file, you ask the
version control system to make it writable for you by @dfn{locking}
it; only one user can lock a given file at any given time.  This
procedure is analogous to, but different from, the locking that Emacs
uses to detect simultaneous editing of ordinary files
268
(@pxref{Interlocking}).  When you commit your changes, that unlocks
269 270 271 272 273 274 275
the file, and the work file becomes read-only again.  Other users may
then lock the file to make their own changes.

  Both locking and merging systems can have problems when multiple
users try to modify the same file at the same time.  Locking systems
have @dfn{lock conflicts}; a user may try to check a file out and be
unable to because it is locked.  In merging systems, @dfn{merge
276 277
conflicts} happen when you commit a change to a file that conflicts
with a change committed by someone else after your checkout.  Both
278
kinds of conflict have to be resolved by human judgment and
279 280 281
communication.  Experience has shown that merging is superior to
locking, both in convenience to developers and in minimizing the
number and severity of conflicts that actually occur.
282 283 284 285

  SCCS always uses locking.  RCS is lock-based by default but can be
told to operate in a merging style.  CVS and Subversion are
merge-based by default but can be told to operate in a locking mode.
286 287
Decentralized version control systems, such as Git and Mercurial, are
exclusively merging-based.
288

289
  VC mode supports both locking and merging version control.  The
290 291 292 293 294 295 296
terms ``commit'' and ``update'' are used in newer version control
systems; older lock-based systems use the terms ``check in'' and
``check out''.  VC hides the differences between them as much as
possible.

@node VCS Changesets
@subsubsection Changeset-based vs File-based Version Control
297

298
@cindex file-based version control
299 300
  On SCCS, RCS, CVS, and other early version control systems, version
control operations are @dfn{file-based}: each file has its own comment
301 302
and revision history separate from that of all other files.  Newer
systems, beginning with Subversion, are @dfn{changeset-based}: a
303
commit may include changes to several files, and the entire set of
304 305
changes is handled as a unit.  Any comment associated with the change
does not belong to a single file, but to the changeset itself.
306

307
@cindex changeset-based version control
308 309 310
  Changeset-based version control is more flexible and powerful than
file-based version control; usually, when a change to multiple files
has to be reversed, it's good to be able to easily identify and remove
311
all of it.
312

313 314 315 316 317
@node VCS Repositories
@subsubsection Decentralized vs Centralized Repositories

@cindex centralized version control
@cindex decentralized version control
318
@cindex distributed version control
319 320 321
  Early version control systems were designed around a
@dfn{centralized} model in which each project has only one repository
used by all developers.  SCCS, RCS, CVS, and Subversion share this
322 323
kind of model.  One of its drawbacks is that the repository is a choke
point for reliability and efficiency.
324

325 326 327 328 329 330 331
  GNU Arch pioneered the concept of @dfn{distributed} or
@dfn{decentralized} version control, later implemented in Git,
Mercurial, and Bazaar.  A project may have several different
repositories, and these systems support a sort of super-merge between
repositories that tries to reconcile their change histories.  In
effect, there is one repository for each developer, and repository
merges take the place of commit operations.
332

333 334 335
  VC helps you manage the traffic between your personal workfiles and
a repository.  Whether the repository is a single master, or one of a
network of peer repositories, is not something VC has to care about.
336 337 338 339 340 341 342 343 344

@node Types of Log File
@subsubsection Types of Log File
@cindex types of log file
@cindex log File, types of
@cindex version control log

  Projects that use a version control system can have two types of log
for changes.  One is the log maintained by the version control system:
345 346 347
each time you commit a change, you fill out a @dfn{log entry} for the
change (@pxref{Log Buffer}).  This is called the @dfn{version control
log}.
348 349 350 351 352 353

  The other kind of log is the file @file{ChangeLog} (@pxref{Change
Log}).  It provides a chronological record of all changes to a large
portion of a program---typically one directory and its subdirectories.
A small program would use one @file{ChangeLog} file; a large program
may have a @file{ChangeLog} file in each major directory.
354 355 356 357 358 359 360
@xref{Change Log}.  Programmers have used change logs since long
before version control systems.

  Changeset-based version systems typically maintain a changeset-based
modification log for the entire system, which makes change log files
somewhat redundant.  One advantage that they retain is that it is
sometimes useful to be able to view the transaction history of a
Xue Fuqiao's avatar
Xue Fuqiao committed
361 362 363
single directory separately from those of other directories.  Another
advantage is that commit logs can't be fixed in many version control
systems.
364 365 366 367 368 369 370 371 372

  A project maintained with version control can use just the version
control log, or it can use both kinds of logs.  It can handle some
files one way and some files the other way.  Each project has its
policy, which you should follow.

  When the policy is to use both, you typically want to write an entry
for each change just once, then put it into both logs.  You can write
the entry in @file{ChangeLog}, then copy it to the log buffer with
373 374 375
@kbd{C-c C-a} when committing the change (@pxref{Log Buffer}).  Or you
can write the entry in the log buffer while committing the change, and
later use the @kbd{C-x v a} command to copy it to @file{ChangeLog}
376 377 378 379 380 381 382 383 384
@iftex
(@pxref{Change Logs and VC,,,emacs-xtra, Specialized Emacs Features}).
@end iftex
@ifnottex
(@pxref{Change Logs and VC}).
@end ifnottex

@node VC Mode Line
@subsection Version Control and the Mode Line
385
@cindex VC mode line indicator
386 387

  When you visit a file that is under version control, Emacs indicates
388 389
this on the mode line.  For example, @samp{Bzr-1223} says that Bazaar
is used for that file, and the current revision ID is 1223.
390

391
@cindex version control status
392
  The character between the back-end name and the revision ID
393 394 395 396 397
indicates the @dfn{version control status} of the work file.  In a
merge-based version control system, a @samp{-} character indicates
that the work file is unmodified, and @samp{:} indicates that it has
been modified.  @samp{!} indicates that the file contains conflicts as
result of a recent merge operation (@pxref{Merging}), or that the file
Xue Fuqiao's avatar
Xue Fuqiao committed
398
was removed from the version control.  Finally, @samp{?} means that
399 400
the file is under version control, but is missing from the working
tree.
401 402 403

  In a lock-based system, @samp{-} indicates an unlocked file, and
@samp{:} a locked file; if the file is locked by another user (for
404
instance, @samp{jim}), that is displayed as @samp{RCS:jim:1.3}.
405
@samp{@@} means that the file was locally added, but not yet committed
406
to the master repository.
407 408

  On a graphical display, you can move the mouse over this mode line
Paul Eggert's avatar
Paul Eggert committed
409
indicator to pop up a tool-tip, which displays a more verbose
410
description of the version control status.  Pressing @kbd{Mouse-1}
411 412
over the indicator pops up a menu of VC commands, identical to
@samp{Tools / Version Control} on the menu bar.
413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428

@vindex auto-revert-check-vc-info
  When Auto Revert mode (@pxref{Reverting}) reverts a buffer that is
under version control, it updates the version control information in
the mode line.  However, Auto Revert mode may not properly update this
information if the version control status changes without changes to
the work file, from outside the current Emacs session.  If you set
@code{auto-revert-check-vc-info} to @code{t}, Auto Revert mode updates
the version control status information every
@code{auto-revert-interval} seconds, even if the work file itself is
unchanged.  The resulting CPU usage depends on the version control
system, but is usually not excessive.

@node Basic VC Editing
@subsection Basic Editing under Version Control

429
@cindex filesets, VC
430
@cindex VC filesets
431
   Most VC commands operate on @dfn{VC filesets}.  A VC fileset is a
432 433 434 435
collection of one or more files that a VC operation acts on.  When you
type VC commands in a buffer visiting a version-controlled file, the
VC fileset is simply that one file.  When you type them in a VC
Directory buffer, and some files in it are marked, the VC fileset
436 437
consists of the marked files (@pxref{VC Directory Mode}).

438 439 440 441 442 443 444
  On modern changeset-based version control systems (@pxref{VCS
Changesets}), VC commands handle multi-file VC filesets as a group.
For example, committing a multi-file VC fileset generates a single
revision, containing the changes to all those files.  On older
file-based version control systems like CVS, each file in a multi-file
VC fileset is handled individually; for example, a commit generates
one revision for each changed file.
445 446

@table @kbd
447
@item C-x v v
448 449
Perform the next appropriate version control operation on the current
VC fileset.
450 451 452 453
@end table

@findex vc-next-action
@kindex C-x v v
454
  The principal VC command is a multi-purpose command, @kbd{C-x v v}
Paul Eggert's avatar
Paul Eggert committed
455
(@code{vc-next-action}), which performs the most appropriate
456 457 458 459 460 461
action on the current VC fileset: either registering it with a version
control system, or committing it, or unlocking it, or merging changes
into it.  The precise actions are described in detail in the following
subsections.  You can use @kbd{C-x v v} either in a file-visiting
buffer or in a VC Directory buffer.

Paul Eggert's avatar
Paul Eggert committed
462
  Note that VC filesets are distinct from the named filesets used
463 464 465
for viewing and visiting files in functional groups
(@pxref{Filesets}).  Unlike named filesets, VC filesets are not named
and don't persist across sessions.
466 467 468 469 470 471 472 473 474 475

@menu
* VC With A Merging VCS::  Without locking: default mode for CVS.
* VC With A Locking VCS::  RCS in its default mode, SCCS, and optionally CVS.
* Advanced C-x v v::       Advanced features available with a prefix argument.
@end menu

@node VC With A Merging VCS
@subsubsection Basic Version Control with Merging

476
  On a merging-based version control system (i.e., most modern ones;
477
@pxref{VCS Merging}), @kbd{C-x v v} does the following:
478 479 480

@itemize @bullet
@item
481
If there is more than one file in the VC fileset and the files have
482
inconsistent version control statuses, signal an error.  (Note,
Paul Eggert's avatar
Paul Eggert committed
483 484
however, that a fileset is allowed to include both newly-added
files and modified files; @pxref{Registering}.)
485 486

@item
487
If none of the files in the VC fileset are registered with a version
488
control system, register the VC fileset, i.e., place it under version
489 490 491
control.  @xref{Registering}.  If Emacs cannot find a system to
register under, it prompts for a repository type, creates a new
repository, and registers the VC fileset with it.
492 493

@item
494
If every work file in the VC fileset is unchanged, do nothing.
495 496

@item
497
If every work file in the VC fileset has been modified, commit the
498
changes.  To do this, Emacs pops up a @file{*vc-log*} buffer; type the
499
desired log entry for the new revision, followed by @kbd{C-c C-c} to
500
commit.  @xref{Log Buffer}.
501 502 503

If committing to a shared repository, the commit may fail if the
repository that has been changed since your last update.  In that
504
case, you must perform an update before trying again.  On a
Glenn Morris's avatar
Glenn Morris committed
505 506 507 508
decentralized version control system, use @kbd{C-x v +}
(@pxref{Pulling / Pushing}) or @kbd{C-x v m} (@pxref{Merging}).
On a centralized version control system, type @kbd{C-x v v} again to
merge in the repository changes.
509 510

@item
511 512 513
Finally, if you are using a centralized version control system, check
if each work file in the VC fileset is up-to-date.  If any file has
been changed in the repository, offer to update it.
514 515
@end itemize

Paul Eggert's avatar
Paul Eggert committed
516
  These rules also apply when you use RCS in its non-locking mode,
517
except that changes are not automatically merged from the repository.
518 519
Nothing informs you if another user has committed changes in the same
file since you began editing it; when you commit your revision, his
520 521
changes are removed (however, they remain in the repository and are
thus not irrevocably lost).  Therefore, you must verify that the
522
current revision is unchanged before committing your changes.  In
523 524 525
addition, locking is possible with RCS even in this mode: @kbd{C-x v
v} with an unmodified file locks the file, just as it does with RCS in
its normal locking mode (@pxref{VC With A Locking VCS}).
526 527 528 529

@node VC With A Locking VCS
@subsubsection Basic Version Control with Locking

530 531
  On a locking-based version control system (such as SCCS, and RCS in
its default mode), @kbd{C-x v v} does the following:
532

533
@itemize @bullet
534
@item
535
If there is more than one file in the VC fileset and the files have
536
inconsistent version control statuses, signal an error.
537 538 539

@item
If each file in the VC fileset is not registered with a version
540 541 542 543
control system, register the VC fileset.  @xref{Registering}.  If
Emacs cannot find a system to register under, it prompts for a
repository type, creates a new repository, and registers the VC
fileset with it.
544 545

@item
Paul Eggert's avatar
Paul Eggert committed
546
If each file is registered and unlocked, lock it and make it writable,
547
so that you can begin to edit it.
548 549

@item
550
If each file is locked by you and contains changes, commit the
551
changes.  To do this, Emacs pops up a @file{*vc-log*} buffer; type the
552 553
desired log entry for the new revision, followed by @kbd{C-c C-c} to
commit (@pxref{Log Buffer}).
554 555

@item
556 557
If each file is locked by you, but you have not changed it, release
the lock and make the file read-only again.
558 559

@item
560
If each file is locked by another user, ask whether you want to
Paul Eggert's avatar
Paul Eggert committed
561
steal the lock.  If you say yes, the file becomes locked by you,
562 563
and a warning message is sent to the user who had formerly locked the
file.
564 565 566
@end itemize

  These rules also apply when you use CVS in locking mode, except
567
that CVS does not support stealing locks.
568 569 570 571

@node Advanced C-x v v
@subsubsection Advanced Control in @kbd{C-x v v}

572
@cindex revision ID in version control
573 574 575 576 577 578 579
  When you give a prefix argument to @code{vc-next-action} (@kbd{C-u
C-x v v}), it still performs the next logical version control
operation, but accepts additional arguments to specify precisely how
to do the operation.

@itemize @bullet
@item
580 581 582 583
@cindex specific version control system
You can specify the name of a version control system.  This is useful
if the fileset can be managed by more than one version control system,
and Emacs fails to detect the correct one.
584 585

@item
586
Otherwise, if using CVS or RCS, you can specify a revision ID.
587

588
If the fileset is modified (or locked), this makes Emacs commit with
589
that revision ID@.  You can create a new branch by supplying an
590
appropriate revision ID (@pxref{Branches}).
591

592 593 594
If the fileset is unmodified (and unlocked), this checks the specified
revision into the working tree.  You can also specify a revision on
another branch by giving its revision or branch ID (@pxref{Switching
595
Branches}).  An empty argument (i.e., @kbd{C-u C-x v v @key{RET}})
Paul Eggert's avatar
Paul Eggert committed
596
checks out the latest (head) revision on the current branch.
597

598
This is silently ignored on a decentralized version control system.
599
Those systems do not let you specify your own revision IDs, nor do
Paul Eggert's avatar
Paul Eggert committed
600
they use the concept of checking out individual files.
601 602 603
@end itemize

@node Log Buffer
604 605
@subsection Features of the Log Entry Buffer

606 607 608
@cindex C-c C-c @r{(Log Edit mode)}
@findex log-edit-done
  When you tell VC to commit a change, it pops up a buffer named
609
@file{*vc-log*}.  In this buffer, you should write a @dfn{log entry}
610
describing the changes you have made (@pxref{Why Version Control?}).
611 612
After you are done, type @kbd{C-c C-c} (@code{log-edit-done}) to exit
the buffer and commit the change, together with your log entry.
613

614 615 616
@cindex Log Edit mode
@cindex mode, Log Edit
@vindex vc-log-mode-hook
Xue Fuqiao's avatar
Xue Fuqiao committed
617
@c FIXME: Mention log-edit-mode-hook here?  --xfq
618
  The major mode for the @file{*vc-log*} buffer is Log Edit mode, a
619 620 621 622
variant of Text mode (@pxref{Text Mode}).  On entering Log Edit mode,
Emacs runs the hooks @code{text-mode-hook} and @code{vc-log-mode-hook}
(@pxref{Hooks}).

623
  In the @file{*vc-log*} buffer, you can write one or more @dfn{header
624 625 626 627 628 629
lines}, specifying additional information to be supplied to the
version control system.  Each header line must occupy a single line at
the top of the buffer; the first line that is not a header line is
treated as the start of the log entry.  For example, the following
header line states that the present change was not written by you, but
by another developer:
630

631 632 633
@smallexample
Author: J. R. Hacker <jrh@@example.com>
@end smallexample
634

635 636 637 638 639
@noindent
Apart from the @samp{Author} header, Emacs recognizes the headers
@samp{Date} (a manually-specified commit time) and @samp{Fixes} (a
reference to a bug fixed by the change).  Not all version control
systems recognize all headers: Bazaar recognizes all three headers,
640
while Git, Mercurial, and Monotone recognize only @samp{Author} and
641 642
@samp{Date}.  If you specify a header for a system that does not
support it, the header is treated as part of the log entry.
643

644
@kindex C-c C-f @r{(Log Edit mode)}
645
@findex log-edit-show-files
646
@kindex C-c C-d @r{(Log Edit mode)}
647
@findex log-edit-show-diff
Paul Eggert's avatar
Paul Eggert committed
648
  While in the @file{*vc-log*} buffer, the current VC fileset is
649 650 651 652 653 654
considered to be the fileset that will be committed if you type
@w{@kbd{C-c C-c}}.  To view a list of the files in the VC fileset,
type @w{@kbd{C-c C-f}} (@code{log-edit-show-files}).  To view a diff
of changes between the VC fileset and the version from which you
started editing (@pxref{Old Revisions}), type @kbd{C-c C-d}
(@code{log-edit-show-diff}).
655

656 657
@kindex C-c C-a @r{(Log Edit mode)}
@findex log-edit-insert-changelog
658 659
  If the VC fileset includes one or more @file{ChangeLog} files
(@pxref{Change Log}), type @kbd{C-c C-a}
660
(@code{log-edit-insert-changelog}) to pull the relevant entries into
661
the @file{*vc-log*} buffer.  If the topmost item in each
662
@file{ChangeLog} was made under your user name on the current date,
663 664
this command searches that item for entries matching the file(s) to be
committed, and inserts them.
665
@ifnottex
666 667 668
If you are using CVS or RCS, see @ref{Change Logs and VC}, for the
opposite way of working---generating ChangeLog entries from the Log
Edit buffer.
669 670
@end ifnottex

671
  To abort a commit, just @emph{don't} type @kbd{C-c C-c} in that
672
buffer.  You can switch buffers and do other editing.  As long as you
673
don't try to make another commit, the entry you were editing remains
674
in the @file{*vc-log*} buffer, and you can go back to that buffer at
675 676 677 678 679 680
any time to complete the commit.

@kindex M-n @r{(Log Edit mode)}
@kindex M-p @r{(Log Edit mode)}
@kindex M-s @r{(Log Edit mode)}
@kindex M-r @r{(Log Edit mode)}
681
  You can also browse the history of previous log entries to duplicate
682 683 684 685 686
a commit comment.  This can be useful when you want to make several
commits with similar comments.  The commands @kbd{M-n}, @kbd{M-p},
@kbd{M-s} and @kbd{M-r} for doing this work just like the minibuffer
history commands (@pxref{Minibuffer History}), except that they are
used outside the minibuffer.
687

688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723
@node Registering
@subsection Registering a File for Version Control

@table @kbd
@item C-x v i
Register the visited file for version control.
@end table

@kindex C-x v i
@findex vc-register
  The command @kbd{C-x v i} (@code{vc-register}) @dfn{registers} each
file in the current VC fileset, placing it under version control.
This is essentially equivalent to the action of @kbd{C-x v v} on an
unregistered VC fileset (@pxref{Basic VC Editing}), except that if the
VC fileset is already registered, @kbd{C-x v i} signals an error
whereas @kbd{C-x v v} performs some other action.

  To register a file, Emacs must choose a version control system.  For
a multi-file VC fileset, the VC Directory buffer specifies the system
to use (@pxref{VC Directory Mode}).  For a single-file VC fileset, if
the file's directory already contains files registered in a version
control system, or if the directory is part of a directory tree
controlled by a version control system, Emacs chooses that system.  In
the event that more than one version control system is applicable,
Emacs uses the one that appears first in the variable
@iftex
@code{vc-handled-backends}.
@end iftex
@ifnottex
@code{vc-handled-backends} (@pxref{Customizing VC}).
@end ifnottex
If Emacs cannot find a version control system to register the file
under, it prompts for a repository type, creates a new repository, and
registers the file into that repository.

  On most version control systems, registering a file with @kbd{C-x v
Paul Eggert's avatar
Paul Eggert committed
724
i} or @kbd{C-x v v} adds it to the working tree but not to the
725 726 727
repository.  Such files are labeled as @samp{added} in the VC
Directory buffer, and show a revision ID of @samp{@@@@} in the mode
line.  To make the registration take effect in the repository, you
728 729
must perform a commit (@pxref{Basic VC Editing}).  Note that a single
commit can include both file additions and edits to existing files.
730 731 732

  On a locking-based version control system (@pxref{VCS Merging}),
registering a file leaves it unlocked and read-only.  Type @kbd{C-x v
733
v} to start editing it.
734 735 736 737 738 739

@node Old Revisions
@subsection Examining And Comparing Old Revisions

@table @kbd
@item C-x v =
740 741 742 743 744 745 746
Compare the work files in the current VC fileset with the versions you
started from (@code{vc-diff}).  With a prefix argument, prompt for two
revisions of the current VC fileset and compare them.  You can also
call this command from a Dired buffer (@pxref{Dired}).

@ifnottex
@item M-x vc-ediff
747
Like @kbd{C-x v =}, but using Ediff.  @xref{Top,, Ediff, ediff, The
748
Ediff Manual}.
749
@end ifnottex
750 751

@item C-x v D
752 753 754
Compare the entire working tree to the revision you started from
(@code{vc-root-diff}).  With a prefix argument, prompt for two
revisions and compare their trees.
755 756 757 758

@item C-x v ~
Prompt for a revision of the current file, and visit it in a separate
buffer (@code{vc-revision-other-window}).
759 760

@item C-x v g
761 762
Display an annotated version of the current file: for each line, show
the latest revision in which it was modified (@code{vc-annotate}).
763 764 765 766
@end table

@findex vc-diff
@kindex C-x v =
767 768 769 770 771 772 773
  @kbd{C-x v =} (@code{vc-diff}) displays a @dfn{diff} which compares
each work file in the current VC fileset to the version(s) from which
you started editing.  The diff is displayed in another window, in a
Diff mode buffer (@pxref{Diff Mode}) named @file{*vc-diff*}.  The
usual Diff mode commands are available in this buffer.  In particular,
the @kbd{g} (@code{revert-buffer}) command performs the file
comparison again, generating a new diff.
774

775 776 777
@kindex C-u C-x v =
  To compare two arbitrary revisions of the current VC fileset, call
@code{vc-diff} with a prefix argument: @kbd{C-u C-x v =}.  This
778 779 780
prompts for two revision IDs (@pxref{VCS Concepts}), and displays a
diff between those versions of the fileset.  This will not work
reliably for multi-file VC filesets, if the version control system is
781
file-based rather than changeset-based (e.g., CVS), since then
782 783 784 785 786 787 788 789 790 791 792 793 794 795
revision IDs for different files would not be related in any
meaningful way.

  Instead of the revision ID, some version control systems let you
specify revisions in other formats.  For instance, under Bazaar you
can enter @samp{date:yesterday} for the argument to @kbd{C-u C-x v =}
(and related commands) to specify the first revision committed after
yesterday.  See the documentation of the version control system for
details.

  If you invoke @kbd{C-x v =} or @kbd{C-u C-x v =} from a Dired buffer
(@pxref{Dired}), the file listed on the current line is treated as the
current VC fileset.

796
@ifnottex
797 798
@findex vc-ediff
  @kbd{M-x vc-ediff} works like @kbd{C-x v =}, except that it uses an
799
Ediff session.  @xref{Top,, Ediff, ediff, The Ediff Manual}.
800 801
@end ifnottex

802 803 804
@findex vc-root-diff
@kindex C-x v D
  @kbd{C-x v D} (@code{vc-root-diff}) is similar to @kbd{C-x v =}, but
805
it displays the changes in the entire current working tree (i.e., the
806 807 808
working tree containing the current VC fileset).  If you invoke this
command from a Dired buffer, it applies to the working tree containing
the directory.
809

810
@vindex vc-diff-switches
811 812 813 814 815
  You can customize the @command{diff} options that @kbd{C-x v =} and
@kbd{C-x v D} use for generating diffs.  The options used are taken
from the first non-@code{nil} value amongst the variables
@code{vc-@var{backend}-diff-switches}, @code{vc-diff-switches}, and
@code{diff-switches} (@pxref{Comparing Files}), in that order.  Here,
816
@var{backend} stands for the relevant version control system,
817
e.g., @code{bzr} for Bazaar.  Since @code{nil} means to check the
818 819 820
next variable in the sequence, either of the first two may use the
value @code{t} to mean no switches at all.  Most of the
@code{vc-@var{backend}-diff-switches} variables default to @code{nil},
821 822 823
but some default to @code{t}; these are for version control systems
whose @code{diff} implementations do not accept common diff options,
such as Subversion.
824 825 826 827 828 829 830 831 832

@findex vc-revision-other-window
@kindex C-x v ~
  To directly examine an older version of a file, visit the work file
and type @kbd{C-x v ~ @var{revision} @key{RET}}
(@code{vc-revision-other-window}).  This retrieves the file version
corresponding to @var{revision}, saves it to
@file{@var{filename}.~@var{revision}~}, and visits it in a separate
window.
833 834 835

@findex vc-annotate
@kindex C-x v g
836 837
  Many version control systems allow you to view files @dfn{annotated}
with per-line revision information, by typing @kbd{C-x v g}
838
(@code{vc-annotate}).  This creates a new ``annotate'' buffer
Paul Eggert's avatar
Paul Eggert committed
839
displaying the file's text, with each line colored to show
840 841 842 843
how old it is.  Red text is new, blue is old, and intermediate colors
indicate intermediate ages.  By default, the color is scaled over the
full range of ages, such that the oldest changes are blue, and the
newest changes are red.
844 845

  When you give a prefix argument to this command, Emacs reads two
846 847 848
arguments using the minibuffer: the revision to display and annotate
(instead of the current file contents), and the time span in days the
color range should cover.
849

850
  From the ``annotate'' buffer, these and other color scaling options are
851 852 853 854 855 856
available from the @samp{VC-Annotate} menu.  In this buffer, you can
also use the following keys to browse the annotations of past revisions,
view diffs, or view log entries:

@table @kbd
@item p
857
Annotate the previous revision, i.e., the revision before the one
858 859
currently annotated.  A numeric prefix argument is a repeat count, so
@kbd{C-u 10 p} would take you back 10 revisions.
860 861

@item n
862
Annotate the next revision, i.e., the revision after the one
863
currently annotated.  A numeric prefix argument is a repeat count.
864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901

@item j
Annotate the revision indicated by the current line.

@item a
Annotate the revision before the one indicated by the current line.
This is useful to see the state the file was in before the change on
the current line was made.

@item f
Show in a buffer the file revision indicated by the current line.

@item d
Display the diff between the current line's revision and the previous
revision.  This is useful to see what the current line's revision
actually changed in the file.

@item D
Display the diff between the current line's revision and the previous
revision for all files in the changeset (for VC systems that support
changesets).  This is useful to see what the current line's revision
actually changed in the tree.

@item l
Show the log of the current line's revision.  This is useful to see
the author's description of the changes in the revision on the current
line.

@item w
Annotate the working revision--the one you are editing.  If you used
@kbd{p} and @kbd{n} to browse to other revisions, use this key to
return to your working revision.

@item v
Toggle the annotation visibility.  This is useful for looking just at
the file contents without distraction from the annotations.
@end table

902
@node VC Change Log
903
@subsection VC Change Log
904 905 906

@table @kbd
@item C-x v l
907
Display the change history for the current fileset
908 909 910 911 912
(@code{vc-print-log}).

@item C-x v L
Display the change history for the current repository
(@code{vc-print-root-log}).
913 914

@item C-x v I
915
Display the changes that a ``pull'' operation will retrieve
916 917 918
(@code{vc-log-incoming}).

@item C-x v O
919
Display the changes that will be sent by the next ``push'' operation
920
(@code{vc-log-outgoing}).
921 922 923 924
@end table

@kindex C-x v l
@findex vc-print-log
925 926 927 928 929
  @kbd{C-x v l} (@code{vc-print-log}) displays a buffer named
@file{*vc-change-log*}, showing the history of changes made to the
current file, including who made the changes, the dates, and the log
entry for each change (these are the same log entries you would enter
via the @file{*vc-log*} buffer; @pxref{Log Buffer}).  Point is
930 931 932 933 934 935 936
centered at the revision of the file currently being visited.  With a
prefix argument, the command prompts for the revision to center on,
and the maximum number of revisions to display.

  If you call @kbd{C-x v l} from a VC Directory buffer (@pxref{VC
Directory Mode}) or a Dired buffer (@pxref{Dired}), it applies to the
file listed on the current line.
937 938

@findex vc-print-root-log
939 940
@findex log-view-toggle-entry-display
  @kbd{C-x v L} (@code{vc-print-root-log}) displays a
941
@file{*vc-change-log*} buffer showing the history of the entire
942 943 944 945 946
version-controlled directory tree (RCS, SCCS, and CVS do not support
this feature).  With a prefix argument, the command prompts for the
maximum number of revisions to display.

  The @kbd{C-x v L} history is shown in a compact form, usually
947 948
showing only the first line of each log entry.  However, you can type
@key{RET} (@code{log-view-toggle-entry-display}) in the
949
@file{*vc-change-log*} buffer to reveal the entire log entry for the
950
revision at point.  A second @key{RET} hides it again.
951

952
  On a decentralized version control system, the @kbd{C-x v I}
953 954
(@code{vc-log-incoming}) command displays a log buffer showing the
changes that will be applied, the next time you run the version
Paul Eggert's avatar
Paul Eggert committed
955
control system's pull command to get new revisions from another
Glenn Morris's avatar
Glenn Morris committed
956
repository (@pxref{Pulling / Pushing}).  This other repository is the default
957 958 959 960
one from which changes are pulled, as defined by the version control
system; with a prefix argument, @code{vc-log-incoming} prompts for a
specific repository.  Similarly, @kbd{C-x v O}
(@code{vc-log-outgoing}) shows the changes that will be sent to
Paul Eggert's avatar
Paul Eggert committed
961
another repository, the next time you run the push command; with a