This is cvs.info, produced by makeinfo version 4.5 from cvs.texinfo.
INFO-DIR-SECTION GNU Packages
START-INFO-DIR-ENTRY
* CVS: (cvs). Concurrent Versions System
END-INFO-DIR-ENTRY
INFO-DIR-SECTION Individual utilities
START-INFO-DIR-ENTRY
* cvs: (cvs)CVS commands. Concurrent Versions System
END-INFO-DIR-ENTRY
File: cvs.info, Node: From files, Next: From other version control systems, Up: Setting up the files
Creating a directory tree from a number of files
------------------------------------------------
When you begin using CVS, you will probably already have several
projects that can be put under CVS control. In these cases the easiest
way is to use the `import' command. An example is probably the easiest
way to explain how to use it. If the files you want to install in CVS
reside in `WDIR', and you want them to appear in the repository as
`$CVSROOT/yoyodyne/RDIR', you can do this:
$ cd WDIR
$ cvs import -m "Imported sources" yoyodyne/RDIR yoyo start
Unless you supply a log message with the `-m' flag, CVS starts an
editor and prompts for a message. The string `yoyo' is a "vendor tag",
and `start' is a "release tag". They may fill no purpose in this
context, but since CVS requires them they must be present. *Note
Tracking sources::, for more information about them.
You can now verify that it worked, and remove your original source
directory.
$ cd ..
$ cvs checkout yoyodyne/RDIR # Explanation below
$ diff -r WDIR yoyodyne/RDIR
$ rm -r WDIR
Erasing the original sources is a good idea, to make sure that you do
not accidentally edit them in WDIR, bypassing CVS. Of course, it would
be wise to make sure that you have a backup of the sources before you
remove them.
The `checkout' command can either take a module name as argument (as
it has done in all previous examples) or a path name relative to
`$CVSROOT', as it did in the example above.
It is a good idea to check that the permissions CVS sets on the
directories inside `$CVSROOT' are reasonable, and that they belong to
the proper groups. *Note File permissions::.
If some of the files you want to import are binary, you may want to
use the wrappers features to specify which files are binary and which
are not. *Note Wrappers::.
File: cvs.info, Node: From other version control systems, Next: From scratch, Prev: From files, Up: Setting up the files
Creating Files From Other Version Control Systems
-------------------------------------------------
If you have a project which you are maintaining with another version
control system, such as RCS, you may wish to put the files from that
project into CVS, and preserve the revision history of the files.
From RCS
If you have been using RCS, find the RCS files--usually a file
named `foo.c' will have its RCS file in `RCS/foo.c,v' (but it
could be other places; consult the RCS documentation for details).
Then create the appropriate directories in CVS if they do not
already exist. Then copy the files into the appropriate
directories in the CVS repository (the name in the repository must
be the name of the source file with `,v' added; the files go
directly in the appropriate directory of the repository, not in an
`RCS' subdirectory). This is one of the few times when it is a
good idea to access the CVS repository directly, rather than using
CVS commands. Then you are ready to check out a new working
directory.
The RCS file should not be locked when you move it into CVS; if it
is, CVS will have trouble letting you operate on it.
From another version control system
Many version control systems have the ability to export RCS files
in the standard format. If yours does, export the RCS files and
then follow the above instructions.
Failing that, probably your best bet is to write a script that
will check out the files one revision at a time using the command
line interface to the other system, and then check the revisions
into CVS. The `sccs2rcs' script mentioned below may be a useful
example to follow.
From SCCS
There is a script in the `contrib' directory of the CVS source
distribution called `sccs2rcs' which converts SCCS files to RCS
files. Note: you must run it on a machine which has both SCCS and
RCS installed, and like everything else in contrib it is
unsupported (your mileage may vary).
From PVCS
There is a script in the `contrib' directory of the CVS source
distribution called `pvcs_to_rcs' which converts PVCS archives to
RCS files. You must run it on a machine which has both PVCS and
RCS installed, and like everything else in contrib it is
unsupported (your mileage may vary). See the comments in the
script for details.
File: cvs.info, Node: From scratch, Prev: From other version control systems, Up: Setting up the files
Creating a directory tree from scratch
--------------------------------------
For a new project, the easiest thing to do is probably to create an
empty directory structure, like this:
$ mkdir tc
$ mkdir tc/man
$ mkdir tc/testing
After that, you use the `import' command to create the corresponding
(empty) directory structure inside the repository:
$ cd tc
$ cvs import -m "Created directory structure" yoyodyne/DIR yoyo start
This will add yoyodyne/DIR as a directory under `$CVSROOT'.
Then, use `add' to add files (and new directories) as they appear.
Check that the permissions CVS sets on the directories inside
`$CVSROOT' are reasonable.
File: cvs.info, Node: Defining the module, Prev: Setting up the files, Up: Starting a new project
Defining the module
===================
The next step is to define the module in the `modules' file. This
is not strictly necessary, but modules can be convenient in grouping
together related files and directories.
In simple cases these steps are sufficient to define a module.
1. Get a working copy of the modules file.
$ cvs checkout CVSROOT/modules
$ cd CVSROOT
2. Edit the file and insert a line that defines the module. *Note
Intro administrative files::, for an introduction. *Note
modules::, for a full description of the modules file. You can
use the following line to define the module `tc':
tc yoyodyne/tc
3. Commit your changes to the modules file.
$ cvs commit -m "Added the tc module." modules
4. Release the modules module.
$ cd ..
$ cvs release -d CVSROOT
File: cvs.info, Node: Revisions, Next: Branching and merging, Prev: Starting a new project, Up: Top
Revisions
*********
For many uses of CVS, one doesn't need to worry too much about
revision numbers; CVS assigns numbers such as `1.1', `1.2', and so on,
and that is all one needs to know. However, some people prefer to have
more knowledge and control concerning how CVS assigns revision numbers.
If one wants to keep track of a set of revisions involving more than
one file, such as which revisions went into a particular release, one
uses a "tag", which is a symbolic revision which can be assigned to a
numeric revision in each file.
* Menu:
* Revision numbers:: The meaning of a revision number
* Versions revisions releases:: Terminology used in this manual
* Assigning revisions:: Assigning revisions
* Tags:: Tags--Symbolic revisions
* Tagging the working directory:: The cvs tag command
* Tagging by date/tag:: The cvs rtag command
* Modifying tags:: Adding, renaming, and deleting tags
* Tagging add/remove:: Tags with adding and removing files
* Sticky tags:: Certain tags are persistent
File: cvs.info, Node: Revision numbers, Next: Versions revisions releases, Up: Revisions
Revision numbers
================
Each version of a file has a unique "revision number". Revision
numbers look like `1.1', `1.2', `1.3.2.2' or even `1.3.2.2.4.5'. A
revision number always has an even number of period-separated decimal
integers. By default revision 1.1 is the first revision of a file.
Each successive revision is given a new number by increasing the
rightmost number by one. The following figure displays a few
revisions, with newer revisions to the right.
+-----+ +-----+ +-----+ +-----+ +-----+
! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 !
+-----+ +-----+ +-----+ +-----+ +-----+
It is also possible to end up with numbers containing more than one
period, for example `1.3.2.2'. Such revisions represent revisions on
branches (*note Branching and merging::); such revision numbers are
explained in detail in *Note Branches and revisions::.
File: cvs.info, Node: Versions revisions releases, Next: Assigning revisions, Prev: Revision numbers, Up: Revisions
Versions, revisions and releases
================================
A file can have several versions, as described above. Likewise, a
software product can have several versions. A software product is
often given a version number such as `4.1.1'.
Versions in the first sense are called "revisions" in this document,
and versions in the second sense are called "releases". To avoid
confusion, the word "version" is almost never used in this document.
File: cvs.info, Node: Assigning revisions, Next: Tags, Prev: Versions revisions releases, Up: Revisions
Assigning revisions
===================
By default, CVS will assign numeric revisions by leaving the first
number the same and incrementing the second number. For example,
`1.1', `1.2', `1.3', etc.
When adding a new file, the second number will always be one and the
first number will equal the highest first number of any file in that
directory. For example, the current directory contains files whose
highest numbered revisions are `1.7', `3.1', and `4.12', then an added
file will be given the numeric revision `4.1'. (When using
client/server CVS, only files that are actually sent to the server are
considered.)
Normally there is no reason to care about the revision numbers--it
is easier to treat them as internal numbers that CVS maintains, and tags
provide a better way to distinguish between things like release 1
versus release 2 of your product (*note Tags::). However, if you want
to set the numeric revisions, the `-r' option to `cvs commit' can do
that. The `-r' option implies the `-f' option, in the sense that it
causes the files to be committed even if they are not modified.
For example, to bring all your files up to revision 3.0 (including
those that haven't changed), you might invoke:
$ cvs commit -r 3.0
Note that the number you specify with `-r' must be larger than any
existing revision number. That is, if revision 3.0 exists, you cannot
`cvs commit -r 1.3'. If you want to maintain several releases in
parallel, you need to use a branch (*note Branching and merging::).
File: cvs.info, Node: Tags, Next: Tagging the working directory, Prev: Assigning revisions, Up: Revisions
Tags-Symbolic revisions
=======================
The revision numbers live a life of their own. They need not have
anything at all to do with the release numbers of your software
product. Depending on how you use CVS the revision numbers might
change several times between two releases. As an example, some of the
source files that make up RCS 5.6 have the following revision numbers:
ci.c 5.21
co.c 5.9
ident.c 5.3
rcs.c 5.12
rcsbase.h 5.11
rcsdiff.c 5.10
rcsedit.c 5.11
rcsfcmp.c 5.9
rcsgen.c 5.10
rcslex.c 5.11
rcsmap.c 5.2
rcsutil.c 5.10
You can use the `tag' command to give a symbolic name to a certain
revision of a file. You can use the `-v' flag to the `status' command
to see all tags that a file has, and which revision numbers they
represent. Tag names must start with an uppercase or lowercase letter
and can contain uppercase and lowercase letters, digits, `-', and `_'.
The two tag names `BASE' and `HEAD' are reserved for use by CVS. It is
expected that future names which are special to CVS will be specially
named, for example by starting with `.', rather than being named
analogously to `BASE' and `HEAD', to avoid conflicts with actual tag
names.
You'll want to choose some convention for naming tags, based on
information such as the name of the program and the version number of
the release. For example, one might take the name of the program,
immediately followed by the version number with `.' changed to `-', so
that CVS 1.9 would be tagged with the name `cvs1-9'. If you choose a
consistent convention, then you won't constantly be guessing whether a
tag is `cvs-1-9' or `cvs1_9' or what. You might even want to consider
enforcing your convention in the `taginfo' file (*note taginfo::).
The following example shows how you can add a tag to a file. The
commands must be issued inside your working directory. That is, you
should issue the command in the directory where `backend.c' resides.
$ cvs tag rel-0-4 backend.c
T backend.c
$ cvs status -v backend.c
===================================================================
File: backend.c Status: Up-to-date
Version: 1.4 Tue Dec 1 14:39:01 1992
RCS Version: 1.4 /u/cvsroot/yoyodyne/tc/backend.c,v
Sticky Tag: (none)
Sticky Date: (none)
Sticky Options: (none)
Existing Tags:
rel-0-4 (revision: 1.4)
For a complete summary of the syntax of `cvs tag', including the
various options, see *Note Invoking CVS::.
There is seldom reason to tag a file in isolation. A more common
use is to tag all the files that constitute a module with the same tag
at strategic points in the development life-cycle, such as when a
release is made.
$ cvs tag rel-1-0 .
cvs tag: Tagging .
T Makefile
T backend.c
T driver.c
T frontend.c
T parser.c
(When you give CVS a directory as argument, it generally applies the
operation to all the files in that directory, and (recursively), to any
subdirectories that it may contain. *Note Recursive behavior::.)
The `checkout' command has a flag, `-r', that lets you check out a
certain revision of a module. This flag makes it easy to retrieve the
sources that make up release 1.0 of the module `tc' at any time in the
future:
$ cvs checkout -r rel-1-0 tc
This is useful, for instance, if someone claims that there is a bug in
that release, but you cannot find the bug in the current working copy.
You can also check out a module as it was at any given date. *Note
checkout options::. When specifying `-r' to any of these commands, you
will need beware of sticky tags; see *Note Sticky tags::.
When you tag more than one file with the same tag you can think
about the tag as "a curve drawn through a matrix of filename vs.
revision number." Say we have 5 files with the following revisions:
file1 file2 file3 file4 file5
1.1 1.1 1.1 1.1 /--1.1* <-*- TAG
1.2*- 1.2 1.2 -1.2*-
1.3 \- 1.3*- 1.3 / 1.3
1.4 \ 1.4 / 1.4
\-1.5*- 1.5
1.6
At some time in the past, the `*' versions were tagged. You can
think of the tag as a handle attached to the curve drawn through the
tagged revisions. When you pull on the handle, you get all the tagged
revisions. Another way to look at it is that you "sight" through a set
of revisions that is "flat" along the tagged revisions, like this:
file1 file2 file3 file4 file5
1.1
1.2
1.1 1.3 _
1.1 1.2 1.4 1.1 /
1.2*----1.3*----1.5*----1.2*----1.1 (--- <--- Look here
1.3 1.6 1.3 \_
1.4 1.4
1.5
File: cvs.info, Node: Tagging the working directory, Next: Tagging by date/tag, Prev: Tags, Up: Revisions
Specifying what to tag from the working directory
=================================================
The example in the previous section demonstrates one of the most
common ways to choose which revisions to tag. Namely, running the `cvs
tag' command without arguments causes CVS to select the revisions which
are checked out in the current working directory. For example, if the
copy of `backend.c' in working directory was checked out from revision
1.4, then CVS will tag revision 1.4. Note that the tag is applied
immediately to revision 1.4 in the repository; tagging is not like
modifying a file, or other operations in which one first modifies the
working directory and then runs `cvs commit' to transfer that
modification to the repository.
One potentially surprising aspect of the fact that `cvs tag'
operates on the repository is that you are tagging the checked-in
revisions, which may differ from locally modified files in your working
directory. If you want to avoid doing this by mistake, specify the
`-c' option to `cvs tag'. If there are any locally modified files, CVS
will abort with an error before it tags any files:
$ cvs tag -c rel-0-4
cvs tag: backend.c is locally modified
cvs [tag aborted]: correct the above errors first!
File: cvs.info, Node: Tagging by date/tag, Next: Modifying tags, Prev: Tagging the working directory, Up: Revisions
Specifying what to tag by date or revision
==========================================
The `cvs rtag' command tags the repository as of a certain date or
time (or can be used to tag the latest revision). `rtag' works
directly on the repository contents (it requires no prior checkout and
does not look for a working directory).
The following options specify which date or revision to tag. See
*Note Common options::, for a complete description of them.
`-D DATE'
Tag the most recent revision no later than DATE.
`-f'
Only useful with the `-D DATE' or `-r TAG' flags. If no matching
revision is found, use the most recent revision (instead of
ignoring the file).
`-r TAG'
Only tag those files that contain existing tag TAG.
The `cvs tag' command also allows one to specify files by revision
or date, using the same `-r', `-D', and `-f' options. However, this
feature is probably not what you want. The reason is that `cvs tag'
chooses which files to tag based on the files that exist in the working
directory, rather than the files which existed as of the given tag/date.
Therefore, you are generally better off using `cvs rtag'. The
exceptions might be cases like:
cvs tag -r 1.4 backend.c
File: cvs.info, Node: Modifying tags, Next: Tagging add/remove, Prev: Tagging by date/tag, Up: Revisions
Deleting, moving, and renaming tags
===================================
Normally one does not modify tags. They exist in order to record
the history of the repository and so deleting them or changing their
meaning would, generally, not be what you want.
However, there might be cases in which one uses a tag temporarily or
accidentally puts one in the wrong place. Therefore, one might delete,
move, or rename a tag.
*WARNING: the commands in this section are dangerous; they permanently
discard historical information and it can be difficult or impossible to
recover from errors. If you are a CVS administrator, you may consider
restricting these commands with the `taginfo' file (*note taginfo::).*
To delete a tag, specify the `-d' option to either `cvs tag' or `cvs
rtag'. For example:
cvs rtag -d rel-0-4 tc
deletes the non-branch tag `rel-0-4' from the module `tc'. In the
event that branch tags are encountered within the repository with the
given name, a warning message will be issued and the branch tag will
not be deleted. If you are absolutely certain you know what you are
doing, the `-B' option may be specified to allow deletion of branch
tags. In that case, any non-branch tags encountered will trigger
warnings and will not be deleted.
*WARNING: Moving branch tags is very dangerous! If you think you need
the `-B' option, think again and ask your CVS administrator about it
(if that isn't you). There is almost certainly another way to
accomplish what you want to accomplish.*
When we say "move" a tag, we mean to make the same name point to
different revisions. For example, the `stable' tag may currently point
to revision 1.4 of `backend.c' and perhaps we want to make it point to
revision 1.6. To move a non-branch tag, specify the `-F' option to
either `cvs tag' or `cvs rtag'. For example, the task just mentioned
might be accomplished as:
cvs tag -r 1.6 -F stable backend.c
If any branch tags are encountered in the repository with the given
name, a warning is issued and the branch tag is not disturbed. If you
are absolutely certain you wish to move the branch tag, the `-B' option
may be specified. In that case, non-branch tags encountered with the
given name are ignored with a warning message.
*WARNING: Moving branch tags is very dangerous! If you think you need
the `-B' option, think again and ask your CVS administrator about it
(if that isn't you). There is almost certainly another way to
accomplish what you want to accomplish.*
When we say "rename" a tag, we mean to make a different name point
to the same revisions as the old tag. For example, one may have
misspelled the tag name and want to correct it (hopefully before others
are relying on the old spelling). To rename a tag, first create a new
tag using the `-r' option to `cvs rtag', and then delete the old name.
(Caution: this method will not work with branch tags.) This leaves the
new tag on exactly the same files as the old tag. For example:
cvs rtag -r old-name-0-4 rel-0-4 tc
cvs rtag -d old-name-0-4 tc
File: cvs.info, Node: Tagging add/remove, Next: Sticky tags, Prev: Modifying tags, Up: Revisions
Tagging and adding and removing files
=====================================
The subject of exactly how tagging interacts with adding and
removing files is somewhat obscure; for the most part CVS will keep
track of whether files exist or not without too much fussing. By
default, tags are applied to only files which have a revision
corresponding to what is being tagged. Files which did not exist yet,
or which were already removed, simply omit the tag, and CVS knows to
treat the absence of a tag as meaning that the file didn't exist as of
that tag.
However, this can lose a small amount of information. For example,
suppose a file was added and then removed. Then, if the tag is missing
for that file, there is no way to know whether the tag refers to the
time before the file was added, or the time after it was removed. If
you specify the `-r' option to `cvs rtag', then CVS tags the files
which have been removed, and thereby avoids this problem. For example,
one might specify `-r HEAD' to tag the head.
On the subject of adding and removing files, the `cvs rtag' command
has a `-a' option which means to clear the tag from removed files that
would not otherwise be tagged. For example, one might specify this
option in conjunction with `-F' when moving a tag. If one moved a tag
without `-a', then the tag in the removed files might still refer to
the old revision, rather than reflecting the fact that the file had
been removed. I don't think this is necessary if `-r' is specified, as
noted above.
File: cvs.info, Node: Sticky tags, Prev: Tagging add/remove, Up: Revisions
Sticky tags
===========
Sometimes a working copy's revision has extra data associated with
it, for example it might be on a branch (*note Branching and
merging::), or restricted to versions prior to a certain date by
`checkout -D' or `update -D'. Because this data persists - that is, it
applies to subsequent commands in the working copy - we refer to it as
"sticky".
Most of the time, stickiness is an obscure aspect of CVS that you
don't need to think about. However, even if you don't want to use the
feature, you may need to know _something_ about sticky tags (for
example, how to avoid them!).
You can use the `status' command to see if any sticky tags or dates
are set:
$ cvs status driver.c
===================================================================
File: driver.c Status: Up-to-date
Version: 1.7.2.1 Sat Dec 5 19:35:03 1992
RCS Version: 1.7.2.1 /u/cvsroot/yoyodyne/tc/driver.c,v
Sticky Tag: rel-1-0-patches (branch: 1.7.2)
Sticky Date: (none)
Sticky Options: (none)
The sticky tags will remain on your working files until you delete
them with `cvs update -A'. The `-A' option merges local changes into
the version of the file from the head of the trunk, removing any sticky
tags, dates, or options. See *Note update:: for more on the operation
of `cvs update'.
The most common use of sticky tags is to identify which branch one
is working on, as described in *Note Accessing branches::. However,
non-branch sticky tags have uses as well. For example, suppose that
you want to avoid updating your working directory, to isolate yourself
from possibly destabilizing changes other people are making. You can,
of course, just refrain from running `cvs update'. But if you want to
avoid updating only a portion of a larger tree, then sticky tags can
help. If you check out a certain revision (such as 1.4) it will become
sticky. Subsequent `cvs update' commands will not retrieve the latest
revision until you reset the tag with `cvs update -A'. Likewise, use
of the `-D' option to `update' or `checkout' sets a "sticky date",
which, similarly, causes that date to be used for future retrievals.
People often want to retrieve an old version of a file without
setting a sticky tag. This can be done with the `-p' option to
`checkout' or `update', which sends the contents of the file to
standard output. For example:
$ cvs update -p -r 1.1 file1 >file1
===================================================================
Checking out file1
RCS: /tmp/cvs-sanity/cvsroot/first-dir/Attic/file1,v
VERS: 1.1
***************
$
However, this isn't the easiest way, if you are asking how to undo a
previous checkin (in this example, put `file1' back to the way it was
as of revision 1.1). In that case you are better off using the `-j'
option to `update'; for further discussion see *Note Merging two
revisions::.
File: cvs.info, Node: Branching and merging, Next: Recursive behavior, Prev: Revisions, Up: Top
Branching and merging
*********************
CVS allows you to isolate changes onto a separate line of
development, known as a "branch". When you change files on a branch,
those changes do not appear on the main trunk or other branches.
Later you can move changes from one branch to another branch (or the
main trunk) by "merging". Merging involves first running `cvs update
-j', to merge the changes into the working directory. You can then
commit that revision, and thus effectively copy the changes onto
another branch.
* Menu:
* Branches motivation:: What branches are good for
* Creating a branch:: Creating a branch
* Accessing branches:: Checking out and updating branches
* Branches and revisions:: Branches are reflected in revision numbers
* Magic branch numbers:: Magic branch numbers
* Merging a branch:: Merging an entire branch
* Merging more than once:: Merging from a branch several times
* Merging two revisions:: Merging differences between two revisions
* Merging adds and removals:: What if files are added or removed?
* Merging and keywords:: Avoiding conflicts due to keyword substitution
File: cvs.info, Node: Branches motivation, Next: Creating a branch, Up: Branching and merging
What branches are good for
==========================
Suppose that release 1.0 of tc has been made. You are continuing to
develop tc, planning to create release 1.1 in a couple of months.
After a while your customers start to complain about a fatal bug. You
check out release 1.0 (*note Tags::) and find the bug (which turns out
to have a trivial fix). However, the current revision of the sources
are in a state of flux and are not expected to be stable for at least
another month. There is no way to make a bug fix release based on the
newest sources.
The thing to do in a situation like this is to create a "branch" on
the revision trees for all the files that make up release 1.0 of tc.
You can then make modifications to the branch without disturbing the
main trunk. When the modifications are finished you can elect to
either incorporate them on the main trunk, or leave them on the branch.
File: cvs.info, Node: Creating a branch, Next: Accessing branches, Prev: Branches motivation, Up: Branching and merging
Creating a branch
=================
You can create a branch with `tag -b'; for example, assuming you're
in a working copy:
$ cvs tag -b rel-1-0-patches
This splits off a branch based on the current revisions in the
working copy, assigning that branch the name `rel-1-0-patches'.
It is important to understand that branches get created in the
repository, not in the working copy. Creating a branch based on
current revisions, as the above example does, will _not_ automatically
switch the working copy to be on the new branch. For information on how
to do that, see *Note Accessing branches::.
You can also create a branch without reference to any working copy,
by using `rtag':
$ cvs rtag -b -r rel-1-0 rel-1-0-patches tc
`-r rel-1-0' says that this branch should be rooted at the revision
that corresponds to the tag `rel-1-0'. It need not be the most recent
revision - it's often useful to split a branch off an old revision (for
example, when fixing a bug in a past release otherwise known to be
stable).
As with `tag', the `-b' flag tells `rtag' to create a branch (rather
than just a symbolic revision name). Note that the numeric revision
number that matches `rel-1-0' will probably be different from file to
file.
So, the full effect of the command is to create a new branch - named
`rel-1-0-patches' - in module `tc', rooted in the revision tree at the
point tagged by `rel-1-0'.
File: cvs.info, Node: Accessing branches, Next: Branches and revisions, Prev: Creating a branch, Up: Branching and merging
Accessing branches
==================
You can retrieve a branch in one of two ways: by checking it out
fresh from the repository, or by switching an existing working copy
over to the branch.
To check out a branch from the repository, invoke `checkout' with
the `-r' flag, followed by the tag name of the branch (*note Creating a
branch::):
$ cvs checkout -r rel-1-0-patches tc
Or, if you already have a working copy, you can switch it to a given
branch with `update -r':
$ cvs update -r rel-1-0-patches tc
or equivalently:
$ cd tc
$ cvs update -r rel-1-0-patches
It does not matter if the working copy was originally on the main
trunk or on some other branch - the above command will switch it to the
named branch. And similarly to a regular `update' command, `update -r'
merges any changes you have made, notifying you of conflicts where they
occur.
Once you have a working copy tied to a particular branch, it remains
there until you tell it otherwise. This means that changes checked in
from the working copy will add new revisions on that branch, while
leaving the main trunk and other branches unaffected.
To find out what branch a working copy is on, you can use the
`status' command. In its output, look for the field named `Sticky tag'
(*note Sticky tags::) - that's CVS's way of telling you the branch, if
any, of the current working files:
$ cvs status -v driver.c backend.c
===================================================================
File: driver.c Status: Up-to-date
Version: 1.7 Sat Dec 5 18:25:54 1992
RCS Version: 1.7 /u/cvsroot/yoyodyne/tc/driver.c,v
Sticky Tag: rel-1-0-patches (branch: 1.7.2)
Sticky Date: (none)
Sticky Options: (none)
Existing Tags:
rel-1-0-patches (branch: 1.7.2)
rel-1-0 (revision: 1.7)
===================================================================
File: backend.c Status: Up-to-date
Version: 1.4 Tue Dec 1 14:39:01 1992
RCS Version: 1.4 /u/cvsroot/yoyodyne/tc/backend.c,v
Sticky Tag: rel-1-0-patches (branch: 1.4.2)
Sticky Date: (none)
Sticky Options: (none)
Existing Tags:
rel-1-0-patches (branch: 1.4.2)
rel-1-0 (revision: 1.4)
rel-0-4 (revision: 1.4)
Don't be confused by the fact that the branch numbers for each file
are different (`1.7.2' and `1.4.2' respectively). The branch tag is the
same, `rel-1-0-patches', and the files are indeed on the same branch.
The numbers simply reflect the point in each file's revision history at
which the branch was made. In the above example, one can deduce that
`driver.c' had been through more changes than `backend.c' before this
branch was created.
See *Note Branches and revisions:: for details about how branch
numbers are constructed.
File: cvs.info, Node: Branches and revisions, Next: Magic branch numbers, Prev: Accessing branches, Up: Branching and merging
Branches and revisions
======================
Ordinarily, a file's revision history is a linear series of
increments (*note Revision numbers::):
+-----+ +-----+ +-----+ +-----+ +-----+
! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 !
+-----+ +-----+ +-----+ +-----+ +-----+
However, CVS is not limited to linear development. The "revision
tree" can be split into "branches", where each branch is a
self-maintained line of development. Changes made on one branch can
easily be moved back to the main trunk.
Each branch has a "branch number", consisting of an odd number of
period-separated decimal integers. The branch number is created by
appending an integer to the revision number where the corresponding
branch forked off. Having branch numbers allows more than one branch
to be forked off from a certain revision.
All revisions on a branch have revision numbers formed by appending
an ordinal number to the branch number. The following figure
illustrates branching with an example.
+-------------+
Branch 1.2.2.3.2 -> ! 1.2.2.3.2.1 !
/ +-------------+
/
/
+---------+ +---------+ +---------+
Branch 1.2.2 -> _! 1.2.2.1 !----! 1.2.2.2 !----! 1.2.2.3 !
/ +---------+ +---------+ +---------+
/
/
+-----+ +-----+ +-----+ +-----+ +-----+
! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 ! <- The main trunk
+-----+ +-----+ +-----+ +-----+ +-----+
!
!
! +---------+ +---------+ +---------+
Branch 1.2.4 -> +---! 1.2.4.1 !----! 1.2.4.2 !----! 1.2.4.3 !
+---------+ +---------+ +---------+
The exact details of how the branch number is constructed is not
something you normally need to be concerned about, but here is how it
works: When CVS creates a branch number it picks the first unused even
integer, starting with 2. So when you want to create a branch from
revision 6.4 it will be numbered 6.4.2. All branch numbers ending in a
zero (such as 6.4.0) are used internally by CVS (*note Magic branch
numbers::). The branch 1.1.1 has a special meaning. *Note Tracking
sources::.
File: cvs.info, Node: Magic branch numbers, Next: Merging a branch, Prev: Branches and revisions, Up: Branching and merging
Magic branch numbers
====================
This section describes a CVS feature called "magic branches". For
most purposes, you need not worry about magic branches; CVS handles
them for you. However, they are visible to you in certain
circumstances, so it may be useful to have some idea of how it works.
Externally, branch numbers consist of an odd number of dot-separated
decimal integers. *Note Revision numbers::. That is not the whole
truth, however. For efficiency reasons CVS sometimes inserts an extra 0
in the second rightmost position (1.2.4 becomes 1.2.0.4, 8.9.10.11.12
becomes 8.9.10.11.0.12 and so on).
CVS does a pretty good job at hiding these so called magic branches,
but in a few places the hiding is incomplete:
* The magic branch number appears in the output from `cvs log'.
* You cannot specify a symbolic branch name to `cvs admin'.
You can use the `admin' command to reassign a symbolic name to a
branch the way RCS expects it to be. If `R4patches' is assigned to the
branch 1.4.2 (magic branch number 1.4.0.2) in file `numbers.c' you can
do this:
$ cvs admin -NR4patches:1.4.2 numbers.c
It only works if at least one revision is already committed on the
branch. Be very careful so that you do not assign the tag to the wrong
number. (There is no way to see how the tag was assigned yesterday).
File: cvs.info, Node: Merging a branch, Next: Merging more than once, Prev: Magic branch numbers, Up: Branching and merging
Merging an entire branch
========================
You can merge changes made on a branch into your working copy by
giving the `-j BRANCHNAME' flag to the `update' subcommand. With one
`-j BRANCHNAME' option it merges the changes made between the greatest
common ancestor (GCA) of the branch and the destination revision (in
the simple case below the GCA is the point where the branch forked) and
the newest revision on that branch into your working copy.
The `-j' stands for "join".
Consider this revision tree:
+-----+ +-----+ +-----+ +-----+
! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 ! <- The main trunk
+-----+ +-----+ +-----+ +-----+
!
!
! +---------+ +---------+
Branch R1fix -> +---! 1.2.2.1 !----! 1.2.2.2 !
+---------+ +---------+
The branch 1.2.2 has been given the tag (symbolic name) `R1fix'. The
following example assumes that the module `mod' contains only one file,
`m.c'.
$ cvs checkout mod # Retrieve the latest revision, 1.4
$ cvs update -j R1fix m.c # Merge all changes made on the branch,
# i.e. the changes between revision 1.2
# and 1.2.2.2, into your working copy
# of the file.
$ cvs commit -m "Included R1fix" # Create revision 1.5.
A conflict can result from a merge operation. If that happens, you
should resolve it before committing the new revision. *Note Conflicts
example::.
If your source files contain keywords (*note Keyword substitution::),
you might be getting more conflicts than strictly necessary. See *Note
Merging and keywords::, for information on how to avoid this.
The `checkout' command also supports the `-j BRANCHNAME' flag. The
same effect as above could be achieved with this:
$ cvs checkout -j R1fix mod
$ cvs commit -m "Included R1fix"
It should be noted that `update -j TAGNAME' will also work but may
not produce the desired result. *Note Merging adds and removals::, for
more.
File: cvs.info, Node: Merging more than once, Next: Merging two revisions, Prev: Merging a branch, Up: Branching and merging
Merging from a branch several times
===================================
Continuing our example, the revision tree now looks like this:
+-----+ +-----+ +-----+ +-----+ +-----+
! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 ! <- The main trunk
+-----+ +-----+ +-----+ +-----+ +-----+
! *
! *
! +---------+ +---------+
Branch R1fix -> +---! 1.2.2.1 !----! 1.2.2.2 !
+---------+ +---------+
where the starred line represents the merge from the `R1fix' branch to
the main trunk, as just discussed.
Now suppose that development continues on the `R1fix' branch:
+-----+ +-----+ +-----+ +-----+ +-----+
! 1.1 !----! 1.2 !----! 1.3 !----! 1.4 !----! 1.5 ! <- The main trunk
+-----+ +-----+ +-----+ +-----+ +-----+
! *
! *
! +---------+ +---------+ +---------+
Branch R1fix -> +---! 1.2.2.1 !----! 1.2.2.2 !----! 1.2.2.3 !
+---------+ +---------+ +---------+
and then you want to merge those new changes onto the main trunk. If
you just use the `cvs update -j R1fix m.c' command again, CVS will
attempt to merge again the changes which you have already merged, which
can have undesirable side effects.
So instead you need to specify that you only want to merge the
changes on the branch which have not yet been merged into the trunk.
To do that you specify two `-j' options, and CVS merges the changes from
the first revision to the second revision. For example, in this case
the simplest way would be
cvs update -j 1.2.2.2 -j R1fix m.c # Merge changes from 1.2.2.2 to the
# head of the R1fix branch
The problem with this is that you need to specify the 1.2.2.2
revision manually. A slightly better approach might be to use the date
the last merge was done:
cvs update -j R1fix:yesterday -j R1fix m.c
Better yet, tag the R1fix branch after every merge into the trunk,
and then use that tag for subsequent merges:
cvs update -j merged_from_R1fix_to_trunk -j R1fix m.c
File: cvs.info, Node: Merging two revisions, Next: Merging adds and removals, Prev: Merging more than once, Up: Branching and merging
Merging differences between any two revisions
=============================================
With two `-j REVISION' flags, the `update' (and `checkout') command
can merge the differences between any two revisions into your working
file.
$ cvs update -j 1.5 -j 1.3 backend.c
will undo all changes made between revision 1.3 and 1.5. Note the
order of the revisions!
If you try to use this option when operating on multiple files,
remember that the numeric revisions will probably be very different
between the various files. You almost always use symbolic tags rather
than revision numbers when operating on multiple files.
Specifying two `-j' options can also undo file removals or
additions. For example, suppose you have a file named `file1' which
existed as revision 1.1, and you then removed it (thus adding a dead
revision 1.2). Now suppose you want to add it again, with the same
contents it had previously. Here is how to do it:
$ cvs update -j 1.2 -j 1.1 file1
U file1
$ cvs commit -m test
Checking in file1;
/tmp/cvs-sanity/cvsroot/first-dir/file1,v <-- file1
new revision: 1.3; previous revision: 1.2
done
$
File: cvs.info, Node: Merging adds and removals, Next: Merging and keywords, Prev: Merging two revisions, Up: Branching and merging
Merging can add or remove files
===============================
If the changes which you are merging involve removing or adding some
files, `update -j' will reflect such additions or removals.
For example:
cvs update -A
touch a b c
cvs add a b c ; cvs ci -m "added" a b c
cvs tag -b branchtag
cvs update -r branchtag
touch d ; cvs add d
rm a ; cvs rm a
cvs ci -m "added d, removed a"
cvs update -A
cvs update -jbranchtag
After these commands are executed and a `cvs commit' is done, file
`a' will be removed and file `d' added in the main branch.
Note that using a single static tag (`-j TAGNAME') rather than a
dynamic tag (`-j BRANCHNAME') to merge changes from a branch will
usually not remove files which were removed on the branch since CVS
does not automatically add static tags to dead revisions. The
exception to this rule occurs when a static tag has been attached to a
dead revision manually. Use the branch tag to merge all changes from
the branch or use two static tags as merge endpoints to be sure that
all intended changes are propagated in the merge.
File: cvs.info, Node: Merging and keywords, Prev: Merging adds and removals, Up: Branching and merging
Merging and keywords
====================
If you merge files containing keywords (*note Keyword
substitution::), you will normally get numerous conflicts during the
merge, because the keywords are expanded differently in the revisions
which you are merging.
Therefore, you will often want to specify the `-kk' (*note
Substitution modes::) switch to the merge command line. By
substituting just the name of the keyword, not the expanded value of
that keyword, this option ensures that the revisions which you are
merging will be the same as each other, and avoid spurious conflicts.
For example, suppose you have a file like this:
+---------+
_! 1.1.2.1 ! <- br1
/ +---------+
/
/
+-----+ +-----+
! 1.1 !----! 1.2 !
+-----+ +-----+
and your working directory is currently on the trunk (revision 1.2).
Then you might get the following results from a merge:
$ cat file1
key $Revision: 1.2 $
. . .
$ cvs update -j br1
U file1
RCS file: /cvsroot/first-dir/file1,v
retrieving revision 1.1
retrieving revision 1.1.2.1
Merging differences between 1.1 and 1.1.2.1 into file1
rcsmerge: warning: conflicts during merge
$ cat file1
<<<<<<< file1
key $Revision: 1.2 $
=======
key $Revision: 1.1.2.1 $
>>>>>>> 1.1.2.1
. . .
What happened was that the merge tried to merge the differences
between 1.1 and 1.1.2.1 into your working directory. So, since the
keyword changed from `Revision: 1.1' to `Revision: 1.1.2.1', CVS tried
to merge that change into your working directory, which conflicted with
the fact that your working directory had contained `Revision: 1.2'.
Here is what happens if you had used `-kk':
$ cat file1
key $Revision: 1.2 $
. . .
$ cvs update -kk -j br1
U file1
RCS file: /cvsroot/first-dir/file1,v
retrieving revision 1.1
retrieving revision 1.1.2.1
Merging differences between 1.1 and 1.1.2.1 into file1
$ cat file1
key $Revision$
. . .
What is going on here is that revision 1.1 and 1.1.2.1 both expand
as plain `Revision', and therefore merging the changes between them
into the working directory need not change anything. Therefore, there
is no conflict.
There is, however, one major caveat with using `-kk' on merges.
Namely, it overrides whatever keyword expansion mode CVS would normally
have used. In particular, this is a problem if the mode had been `-kb'
for a binary file. Therefore, if your repository contains binary
files, you will need to deal with the conflicts rather than using `-kk'.