NAME
gitcvs-migration - git for CVS users
SYNOPSIS
git cvsimport *
DESCRIPTION
Git differs from CVS in that every working tree contains a repository
with a full copy of the project history, and no repository is
inherently more important than any other. However, you can emulate the
CVS model by designating a single shared repository which people can
synchronize with; this document explains how to do that.
Some basic familiarity with git is required. Having gone through
gittutorial(7) and gitglossary(7) should be sufficient.
DEVELOPING AGAINST A SHARED REPOSITORY
Suppose a shared repository is set up in /pub/repo.git on the host
foo.com. Then as an individual committer you can clone the shared
repository over ssh with:
$ git clone foo.com:/pub/repo.git/ my-project
$ cd my-project
and hack away. The equivalent of cvs update is
$ git pull origin
which merges in any work that others might have done since the clone
operation. If there are uncommitted changes in your working tree,
commit them first before running git pull.
Note
The pull command knows where to get updates from because of certain
configuration variables that were set by the first git clone
command; see git config -l and the git-config(1) man page for
details.
You can update the shared repository with your changes by first
committing your changes, and then using the git push command:
$ git push origin master
to "push" those commits to the shared repository. If someone else has
updated the repository more recently, git push, like cvs commit, will
complain, in which case you must pull any changes before attempting the
push again.
In the git push command above we specify the name of the remote branch
to update (master). If we leave that out, git push tries to update any
branches in the remote repository that have the same name as a branch
in the local repository. So the last push can be done with either of:
$ git push origin
$ git push foo.com:/pub/project.git/
as long as the shared repository does not have any branches other than
master.
SETTING UP A SHARED REPOSITORY
We assume you have already created a git repository for your project,
possibly created from scratch or from a tarball (see gittutorial(7)),
or imported from an already existing CVS repository (see the next
section).
Assume your existing repo is at /home/alice/myproject. Create a new
"bare" repository (a repository without a working tree) and fetch your
project into it:
$ mkdir /pub/my-repo.git
$ cd /pub/my-repo.git
$ git --bare init --shared
$ git --bare fetch /home/alice/myproject master:master
Next, give every team member read/write access to this repository. One
easy way to do this is to give all the team members ssh access to the
machine where the repository is hosted. If you don't want to give them
a full shell on the machine, there is a restricted shell which only
allows users to do git pushes and pulls; see git-shell(1).
Put all the committers in the same group, and make the repository
writable by that group:
$ chgrp -R $group /pub/my-repo.git
Make sure committers have a umask of at most 027, so that the
directories they create are writable and searchable by other group
members.
IMPORTING A CVS ARCHIVE
First, install version 2.1 or higher of cvsps from
http://www.cobite.com/cvsps/ and make sure it is in your path. Then cd
to a checked out CVS working directory of the project you are
interested in and run git-cvsimport(1):
$ git cvsimport -C <destination> <module>
This puts a git archive of the named CVS module in the directory
<destination>, which will be created if necessary.
The import checks out from CVS every revision of every file. Reportedly
cvsimport can average some twenty revisions per second, so for a
medium-sized project this should not take more than a couple of
minutes. Larger projects or remote repositories may take longer.
The main trunk is stored in the git branch named origin, and additional
CVS branches are stored in git branches with the same names. The most
recent version of the main trunk is also left checked out on the master
branch, so you can start adding your own changes right away.
The import is incremental, so if you call it again next month it will
fetch any CVS updates that have been made in the meantime. For this to
work, you must not modify the imported branches; instead, create new
branches for your own changes, and merge in the imported branches as
necessary.
If you want a shared repository, you will need to make a bare clone of
the imported directory, as described above. Then treat the imported
directory as another development clone for purposes of merging
incremental imports.
ADVANCED SHARED REPOSITORY MANAGEMENT
Git allows you to specify scripts called "hooks" to be run at certain
points. You can use these, for example, to send all commits to the
shared repository to a mailing list. See githooks(5).
You can enforce finer grained permissions using update hooks. See
Controlling access to branches using update hooks[1].
PROVIDING CVS ACCESS TO A GIT REPOSITORY
It is also possible to provide true CVS access to a git repository, so
that developers can still use CVS; see git-cvsserver(1) for details.
ALTERNATIVE DEVELOPMENT MODELS
CVS users are accustomed to giving a group of developers commit access
to a common repository. As we've seen, this is also possible with git.
However, the distributed nature of git allows other development models,
and you may want to first consider whether one of them might be a
better fit for your project.
For example, you can choose a single person to maintain the project's
primary public repository. Other developers then clone this repository
and each work in their own clone. When they have a series of changes
that they're happy with, they ask the maintainer to pull from the
branch containing the changes. The maintainer reviews their changes and
pulls them into the primary repository, which other developers pull
from as necessary to stay coordinated. The Linux kernel and other
projects use variants of this model.
With a small group, developers may just pull changes from each other's
repositories without the need for a central maintainer.
SEE ALSO
gittutorial(7), gittutorial-2(7), gitcore-tutorial(7), gitglossary(7),
Everyday Git[2], The Git User's Manual[3]
GIT
Part of the git(1) suite.
NOTES
1. Controlling access to branches using update hooks
file:///usr/share/doc/git-doc/howto/update-hook-example.txt
2. Everyday Git
file:///usr/share/doc/git-doc/everyday.html
3. The Git User's Manual
file:///usr/share/doc/git-doc/user-manual.html