gitcvs-migration






gitcvs‐migration − Git for CVS users



git cvsimport *




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.



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











                             ‐2‐


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.



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.












                             ‐3‐




     Note

     These instructions use the git−cvsimport script which
     ships with git, but other importers may provide better
     results. See the note in git‐cvsimport(1) for other
     options.

First, install version 2.1 or higher of cvsps from
https://github.com/andreyvit/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.



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].










                             ‐4‐




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.



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.



gittutorial(7), gittutorial‐2(7), gitcore‐tutorial(7),
gitglossary(7), giteveryday(7), The Git User’s Manual[2]



Part of the git(1) suite



 1. Controlling access to branches using update hooks
        file:///usr/share/doc/git‐doc/howto/update‐hook‐example.html

 2. The Git User’s Manual
        file:///usr/share/doc/git‐doc/user‐manual.html