1git for CVS users 2================= 3 4Git differs from CVS in that every working tree contains a repository with 5a full copy of the project history, and no repository is inherently more 6important than any other. However, you can emulate the CVS model by 7designating a single shared repository which people can synchronize with; 8this document explains how to do that. 9 10Some basic familiarity with git is required. This 11link:tutorial.html[tutorial introduction to git] should be sufficient. 12 13Developing against a shared repository 14-------------------------------------- 15 16Suppose a shared repository is set up in /pub/repo.git on the host 17foo.com. Then as an individual committer you can clone the shared 18repository over ssh with: 19 20------------------------------------------------ 21$ git clone foo.com:/pub/repo.git/ my-project 22$ cd my-project 23------------------------------------------------ 24 25and hack away. The equivalent of `cvs update` is 26 27------------------------------------------------ 28$ git pull origin 29------------------------------------------------ 30 31which merges in any work that others might have done since the clone 32operation. If there are uncommitted changes in your working tree, commit 33them first before running git pull. 34 35[NOTE] 36================================ 37The first `git clone` places the following in the 38`my-project/.git/remotes/origin` file, and that's why the previous step 39and the next step both work. 40------------ 41URL: foo.com:/pub/project.git/ 42Pull: refs/heads/master:refs/remotes/origin/master 43------------ 44================================ 45 46You can update the shared repository with your changes by first committing 47your changes, and then using the gitlink:git-push[1] command: 48 49------------------------------------------------ 50$ git push origin master 51------------------------------------------------ 52 53to "push" those commits to the shared repository. If someone else has 54updated the repository more recently, `git push`, like `cvs commit`, will 55complain, in which case you must pull any changes before attempting the 56push again. 57 58In the `git push` command above we specify the name of the remote branch 59to update (`master`). If we leave that out, `git push` tries to update 60any branches in the remote repository that have the same name as a branch 61in the local repository. So the last `push` can be done with either of: 62 63------------ 64$ git push origin 65$ git push foo.com:/pub/project.git/ 66------------ 67 68as long as the shared repository does not have any branches 69other than `master`. 70 71Setting Up a Shared Repository 72------------------------------ 73 74We assume you have already created a git repository for your project, 75possibly created from scratch or from a tarball (see the 76link:tutorial.html[tutorial]), or imported from an already existing CVS 77repository (see the next section). 78 79Assume your existing repo is at /home/alice/myproject. Create a new "bare" 80repository (a repository without a working tree) and fetch your project into 81it: 82 83------------------------------------------------ 84$ mkdir /pub/my-repo.git 85$ cd /pub/my-repo.git 86$ git --bare init-db --shared 87$ git --bare fetch /home/alice/myproject master:master 88------------------------------------------------ 89 90Next, give every team member read/write access to this repository. One 91easy way to do this is to give all the team members ssh access to the 92machine where the repository is hosted. If you don't want to give them a 93full shell on the machine, there is a restricted shell which only allows 94users to do git pushes and pulls; see gitlink:git-shell[1]. 95 96Put all the committers in the same group, and make the repository 97writable by that group: 98 99------------------------------------------------ 100$ chgrp -R $group /pub/my-repo.git 101------------------------------------------------ 102 103Make sure committers have a umask of at most 027, so that the directories 104they create are writable and searchable by other group members. 105 106Importing a CVS archive 107----------------------- 108 109First, install version 2.1 or higher of cvsps from 110link:http://www.cobite.com/cvsps/[http://www.cobite.com/cvsps/] and make 111sure it is in your path. Then cd to a checked out CVS working directory 112of the project you are interested in and run gitlink:git-cvsimport[1]: 113 114------------------------------------------- 115$ git cvsimport -C <destination> 116------------------------------------------- 117 118This puts a git archive of the named CVS module in the directory 119<destination>, which will be created if necessary. 120 121The import checks out from CVS every revision of every file. Reportedly 122cvsimport can average some twenty revisions per second, so for a 123medium-sized project this should not take more than a couple of minutes. 124Larger projects or remote repositories may take longer. 125 126The main trunk is stored in the git branch named `origin`, and additional 127CVS branches are stored in git branches with the same names. The most 128recent version of the main trunk is also left checked out on the `master` 129branch, so you can start adding your own changes right away. 130 131The import is incremental, so if you call it again next month it will 132fetch any CVS updates that have been made in the meantime. For this to 133work, you must not modify the imported branches; instead, create new 134branches for your own changes, and merge in the imported branches as 135necessary. 136 137Advanced Shared Repository Management 138------------------------------------- 139 140Git allows you to specify scripts called "hooks" to be run at certain 141points. You can use these, for example, to send all commits to the shared 142repository to a mailing list. See link:hooks.html[Hooks used by git]. 143 144You can enforce finer grained permissions using update hooks. See 145link:howto/update-hook-example.txt[Controlling access to branches using 146update hooks]. 147 148Providing CVS Access to a git Repository 149---------------------------------------- 150 151It is also possible to provide true CVS access to a git repository, so 152that developers can still use CVS; see gitlink:git-cvsserver[1] for 153details. 154 155Alternative Development Models 156------------------------------ 157 158CVS users are accustomed to giving a group of developers commit access to 159a common repository. As we've seen, this is also possible with git. 160However, the distributed nature of git allows other development models, 161and you may want to first consider whether one of them might be a better 162fit for your project. 163 164For example, you can choose a single person to maintain the project's 165primary public repository. Other developers then clone this repository 166and each work in their own clone. When they have a series of changes that 167they're happy with, they ask the maintainer to pull from the branch 168containing the changes. The maintainer reviews their changes and pulls 169them into the primary repository, which other developers pull from as 170necessary to stay coordinated. The Linux kernel and other projects use 171variants of this model. 172 173With a small group, developers may just pull changes from each other's 174repositories without the need for a central maintainer.