Using Git for Samba Development

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The previous pages based on the git-svn mirror can be found at Using Git-SVN for Samba Development (deprecated)


Contents

Overview

Samba source code is now hosted in a shared git repository to which all existing Samba Team members are allow to push to. If you are a Team member and do not have an account on git.samba.org, please email the team list and let the appropriate people know. This shared repository has the same work flow as was used when the SCM of choice was Subversion. In other words, you develop in your local tree and push to the repo although is not necessary to push after every commit. This should be a familiar work flow for those who have used svk.


Git Installation

The examples in the following sections are based off of the tools and syntax used by git v1.5.3 or later which is the recommended version for Samba. Either apt-get, yum, or make install the tools. See Git documentation for more details on this part.

If you are on OS X, both MacPorts and Fink contain working binary packages of Git. Building Git from source on OS X works fine, but resolving the chain of dependencies for asciidoc (which is needed to build the man pages) is very painful.

Basic Samba Git

The master git repository is located at git://git.samba.org/samba.git. There is also a GitWeb installation.

WARNING: git://git.samba.org/samba.git was previously a git-svn mirror. The mirror has been moved to git://git.samba.org/samba-svnmirror.git.

Step Zero is to set your name and email address for commits:

 $ git config --global user.email Your.Email@domain.com
 $ git config --global user.name "Your Real Name"

Next, clone the repository:

 $ git clone git://git.samba.org/samba.git samba
 Initialized empty Git repository in /home/AD/gcarter/src/git/tmp/samba/.git/
 remote: Generating pack...
 remote: Done counting 440544 objects.
 remote: Deltifying 440544 objects...
 remote:  100% (440544/440544) done
 Indexing 440544 objects...
 remote: Total 440544 (delta 340808), reused 436199 (delta 336480)
  100% (440544/440544) done
 Resolving 340808 deltas...
  100% (340808/340808) done
 $ cd samba

List local and remote branches:

 $ git branch
   * v3-2-test
 $ git branch -r
   origin/HEAD
   origin/v3-0-stable
   origin/v3-0-test
   origin/v3-2-stable
   origin/v3-2-test

Listing tags matching release-3-0-3*

 $ git tag -l release-3-0-3*
 release-3-0-3
 release-3-0-3pre1
 release-3-0-3pre2
 release-3-0-3rc1

Creating your own working branch from v3-2-test:

 $ git checkout -b my_branch origin/v3-2-test
 Branch my_branch set up to track remote branch refs/remotes/origin/v3-2-test.
 Switched to a new branch "my_branch"

Do your own local work:

 $ mkdir git-test
 $ echo "hello" > git-test/README

View status of changes

 $ git status
 # On branch my_branch
 # Untracked files:
 #   (use "git add <file>..." to include in what will be committed)
 # 
 #       git-test/
 nothing added to commit but untracked files present (use "git add" to track)

Add our new file to the local branch index:

 $ git add git-test
 $ git status
 # On branch my_branch
 # Changes to be committed:
 #   (use "git reset HEAD <file>..." to unstage)
 #
 #       new file:   git-test/README
 #

Commit changes

 $ git commit -m "Example file for HOWTO"
 Created commit ad9a1eb: Example file for HOWTO
  1 files changed, 1 insertions(+), 0 deletions(-)
  create mode 100644 git-test/README

Do some more work and commit local changes....

Now fetch the remote branch history:

 $ git fetch 

Merging remote branch changes:

 $ git merge origin/v3-2-test
 Already up-to-date.

To present your patchset properly to other developers, please rebase your patches against the branch you are developing against. In particular, if you are developing for Samba 3, please regularly do a

 $ git rebase origin/v3-2-test

Obviously replace "origin/v3-2-test" by "origin/master", "origin/v3-4-test" or whatever branch you are developing against. If you have created a mess in your local patch queue, "git rebase -i" might help you out.

Push the changes to the shared repository

 $ git push ssh://git.samba.org/data/git/samba.git my_branch:v3-2-test
 updating 'refs/heads/v3-2-test' using 'refs/heads/my_branch'
   from f2252e041e075e19bf27e53ab3ed62f39bc8b3e2
   to   ad9a1eb599c125964ac3e198d3003841edb4c54e
 Generating pack...
 Done counting 5 objects.
 Result has 4 objects.
 Deltifying 4 objects...
  100% (4/4) done
 Writing 4 objects...
  100% (4/4) done
 Total 4 (delta 1), reused 0 (delta 0)
 refs/heads/v3-2-test: f2252e041e075e19bf27e53ab3ed62f39bc8b3e2 -> ad9a1eb599c125964ac3e198d3003841edb4c54e

Some Git Tricks

When you have quite some changes to commit, but you want to split them in logically coherent commits you can do that with the following invocation:

 $ git commit -i

When you have commits you want to push, but you want to have the commits to compile on their own, you can insert x make -j after each commit to check if they do compile one after the other with:

 $ git rebase -i

Last, but not least, when you want to discard part of your changes before committing, you can use:

 $ git reset -p

Explanation of Branches

The simplest way to explain the existing shared branches is to associate them with the previous SVN ones.

  • The *-unstable tags point to the matching SAMBA_X_X branch (e.g. SAMBA_3_2 or SAMBA_4_0) at the time of the migration. These are now tags and not branches, so you cannot push to them. Instead, your local work should be done in a local branch and pushed when completed. There is no need to push work in progress any longer unless you require some specific testing by the buildfarm.
  • The master branch is the new combined Samba 3 (was: v3-devel) and Samba 4 (was: v4-0-test) development branch. It includes Samba 3 sources in a directory called source3 and Samba 4 sources in a directory called source4. Anyone may check into this branch.
  • The *-test branches correspond to the release series dev branch (e.g. SAMBA_3_2_0). Anyone may check into these branches.
  • The *-stable branches are used for release purposes similar to the SAMBA_X_X_RELEASE branches in SVN. These are under the control of the current release manager for a given release series.
  • The v3-devel branch was the former Samba 3 development branch. It has been turned readonly during the introduction of the master branch. The master branch replaces v3-devel.
  • The v4-0-test branch was the former Samba 4 development branch. It has been turned readonly during the introduction of the master branch. The master branch replaces v4-0-test.

Creating patches if you don't have write access to git.samba.org repositories

If you don't have write access to git.samba.org, using git push to get your changes into Samba is obviously not going to work. In this case, you should create patches. Now, assuming your patches are the last three commits on your current local git branch, this is the easiest way to create patches from them:

 $ git format-patch -3

This will create three patch files in your current directory that you can then send to the samba-technical mailing list.

Note that if you have a number of patches against a specific samba.git branch and don't feel like counting them, the following works as well (e.g. against the master branch):

 $ git format-patch origin/master

This will create one patch file for every patch that is in your local branch but not in origin/master.

If you have more patches which belong together it's sometimes useful to export them into one file:

 $ git format-patch --stdout origin/master > master-featureX-01.patches.txt

FAQ

Q. How do I revert a commit?

A. The "git reset" command allows you to reset the HEAD of the branch to any given point in history. To go back one commit, run "git reset HEAD^". This will keep your local changes and you can make any additional changes before re-commiting the new work. Also see the "git commit --amend" command and the "git reset" man page for other examples.


Q. Is there a shorthand for git push <URL> <local_repo:remote_repo>?

A. Yes. You can define a [remote "upstream"] section in your local repos .git/config file.

 $ git config remote.origin.url ssh://git.samba.org/data/git/samba.git
 $ git config remote.origin.push my_branch:v3-2-test
 $ cat .git/config
 ...
 [remote "origin"]
         url = ssh://git.samba.org/data/git/samba.git
         fetch = +refs/heads/*:refs/remotes/origin/*
         push = my_branch:v3-2-test
 [branch "my_branch"]
         remote = origin
         merge = refs/heads/v3-2-test


Q. How can I have access to the old CVS and SVN imported repositories via GIT without creating additional cloned repos?

A. You can add remote tracking repositories using "git remote":

 $ git remote add cvs git://git.samba.org/import/samba-cvsimport.git
 $ git fetch cvs
 remote: Generating pack...
 remote: Done counting 7070 objects.
 Result has 5004 objects.
 remote: Deltifying 5004 objects...
 remote:  100% (5004/5004) done
 Indexing 5004 objects...
 remote: Total 5004 (delta 3836), reused 4098 (delta 3044)
  100% (5004/5004) done
 Resolving 3836 deltas...
  100% (3836/3836) done
 461 objects were added to complete this thin pack.
 * refs/remotes/cvs/APPLIANCE_HEAD: storing branch 'APPLIANCE_HEAD' of git://  git.samba.org/import/samba-cvsimport
   commit: af0e201

You can then see the remote branches using "git branch -r" and work with them in the same way you did for the "origin" branches obtained in the initial "git clone".

Q. How can I maintain a feature branch against the upstream Samba branches?

A. You clone the Samba repository as per the instructions above. Then you make a new feature branch from v3-2-test:

$ git branch feature/foo v3-2-test

Now you do your development in your feature branch. Any time the v3-2-test branch gets too different to the code in your feature branch you should rebase your feature branch. The rebase rewinds your feature branch to the point there it was branched. Then it updates you feature branch to the HEAD of the v3-2-test branch and re-applies your changes.

$ git rebase v3-2-test
First, rewinding head to replay your work on top of it...
HEAD is now at 357f003... Add WERR_SERVICE_ALREADY_RUNNING.
...
Wrote tree 02299ef7c1cfa093248bfd9c6e3812805718845e
Committed: e20a8c521d7860d9b7bd724ed5ea19c7306530ab

Rebase works best when you use it for local branches that are never pushed to a public repository, see Why won't "git push" work after I rebased a branch?.

Suggestions for .gitconfig

In order to comply with Samba coding standards and not add new trailing whitespace (see: Samba Coding Standards Document) it is suggested to put:

[apply]
       whitespace = strip

into your $HOME/.gitconfig file.

That way, whenever you apply a patch using git-am or rebase your work on top of the upstream trees with git-rebase, all newly added whitespace is nicely removed automatically.

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