Introduction

There are a couple of FreeBSD git repositories that have been converted with various programs and various parameters. This page describes the "official" git-branches of the FreeBSD project that should be used as common repositories to base other work on.

The repositories are provided as a read-only mirror of the state of the Subversion src, doc and, ports repositories at http://svn.FreeBSD.org/base, http://svn.FreeBSD.org/doc, and http://svn.FreeBSD.org/ports respectively. Using git to commit changes to these repositories is not officially supported (but doable), instead it is supposed to serve as a collaboration point by using additional tools like Github, Gitorious, or Gerrit, etc.

Bear in mind that git will not replace Subversion for use in FreeBSD and the repository is only offered on a best-effort basis. The steps to redo the conversion are outlined below, so that people can move the process in-house should they see the need for it.

The Repositories

The beta repository-mirrors are updated at least hourly, should they lag the svn repository by more than a day, please contact <uqs@FreeBSD.org> (monitoring still needs to be put into place, help wanted btw).

• git://github.com/freebsd/freebsd.git

• git://github.com/freebsd/freebsd-doc.git

• git://github.com/freebsd/freebsd-ports.git (the preferred sources)

• git://git-beta.freebsd.org/freebsd-base.git
• git://git-beta.freebsd.org/freebsd-doc.git
• git://git-beta.freebsd.org/freebsd-ports.git (the canonical sources)

• https://code.google.com/p/freebsd (stale, Google Code chokes on pushes that are too large, devs informed and aware of the issue)

The obsolete, non-compatible repositories are:

• A git-svn clone of head and a couple of stable branches, but with truncated history.
  • git://gitorious.org/freebsd/freebsd.git

• A git-svn clone of head, with complete history. It's what you get when doing: git svn clone -Thead svn+ssh://svn.freebsd.org/base/

  • git://git.freebsd.your.org/freebsd-head
  • rsync://repos.freebsd.your.org/freebsd-head.git/
  • git://github.com/freebsd/freebsd-head.git
  • git://gitorious.org/freebsd/freebsd-head.git

  • https://code.google.com/p/freebsd-head

Known Problems

• SVN merges for single revisions (that span only parts of the tree then), are not really representable as merges in git and instead are called cherry-picks there. The converter tries to be smart about whole tree merges however -- this heuristic is only activated for the head/, user/, and projects/ branches. A whole-tree merge of project/foo into head/ should thus be correctly represented in git. Merges from head/ to stable/ or from contrib/ to head/ will be plain commits, i.e. "cherry-picks".

Quick Start

$ git clone --config remote.origin.fetch='+refs/notes/*:refs/notes/*' git://github.com/freebsd/freebsd.git
$ cd freebsd && git pull   # For some reason, the notes will not be fetched during the clone operation ...
$ hack, hack, hack
$ git commit

Advanced, useful examples to show the diff between a subdir of a branch, or the commits that introduced these diffs. It is basically what svn mergeinfo --show-revs=eligible does. See git-log(1) for more info.

$ git diff origin/stable/9 master -- usr.sbin/acpi
$ git log --graph --format=oneline --right-only --cherry-pick --no-merges origin/stable/9...origin/master -- usr.sbin/acpi

See any other git howto or documentation if you're stuck on the basics. A useful reference for the issue with notes is http://git-scm.com/2010/08/25/notes.html.

Collaboration

There is no endorsed way yet of how users should collaborate with developers on changes they have made. Please bear in mind that git is strictly ancillary at this point and not many committers are using it.

Having your patches/feature-branches published on github for a FreeBSD committer to comment on and pull from seems like the first sensible step. Sending a patch-bomb with git send-email might be an alternative to github or for developers that do not want to use git.

Receiving and integrating these patches can be done in various ways, see below.

Integration

Integrating the changes back into svn is not as trivial as using git-svn(1), as the current repository doesn't have the required meta-information. Instead patches can be applied to a subversion workspace just like any other regular patch.

A more sophisticated approach would be to share the svn and the git workspaces, which can be done by putting .svn in .gitignore and vice versa. This requires subversion 1.7 and you need to know how to recover from out-of-sync workspaces in both subversion and git, or be extra careful to avoid this situation.

Using git-svn (FreeBSD committers only)

The repositories on github also have a branch that is the result of a conversion using git-svn, i.e. the necessary conversion has already been made. To use this, you simply need to:

$ git clone git://github.com/freebsd/freebsd.git
$ cd freebsd
$ git svn init -Thead svn+ssh://svn.freebsd.org/base .
# People w/o write access to SVN can use this instead: git svn init -Thead --rewrite-root=svn+ssh://svn.freebsd.org/base svn://svn.freebsd.org/base .
$ git update-ref refs/remotes/trunk `git show-ref origin/svn_head|cut -d" " -f1` # git-svn really needs this branch
$ git svn fetch  # This will now reconstruct the necessary metadata and should be pretty fast
$ git checkout trunk; git branch -D master # delete master
$ git checkout -b master trunk # and have master hang off trunk
$ git svn rebase # this will now update everything to the latest state in head

Now you can periodically sync to svn using git svn rebase and you can push small changes back to svn using git svn dcommit, but read on.

Things to keep in mind:

• Never git merge branches, unless you know what you're doing.

• Always git rebase your work on top of master, then git svn dcommit can push the top commits to svn.

• Always double-check with git svn dcommit -n to see what would happen.

• While you can use git add for new files just fine, you won't be able to push those upstream, you can however use the patch, apply it to some subversion checkout and do the commit there. This is a shortcoming of our very own Subversion hacks, but hey, it's better than nothing!

• While git-svn now allows you to set svn:mergeinfo when committing, this is so fragile that the FreeBSD projects discourages its use. Please use svn(1) for merging, sorry.

Experimental git-svn bootstrap

There is an experimental git-svn bootstrap for quickly getting a complete git-svn enabled repository of your own.

Visit https://github.com/knu/freebsd and follow the instructions described in the README file.

FAQ

• I want authornames!

  • Good for you, and this has been done but abandoned again for various reasons: There's no authoritative, complete and stable mapping of svn users to "Name <email>" pairs. Especially for people without access to freefall. Random contributors are more likely to have a conversion using the current parameters.

• Why the full history and not only since day X
  • It would make the history incompatible with other people's repository and the space savings are simply not worth the hassle. As of Oct/2012, all revisions make up about 933MB.

Everything done is so that everybody can verify the integrity of the conversion using the tools mentioned in this article. Hence the focus on repeat-ability of the process.

Verification

Content

Verifying that the git export is identical to the SVN tree (in content), can be done like this:

$ svn export --ignore-keywords svn://svn.freebsd.org/base/head freebsd.svn
...
Exported revision 243246.
$ git clone --config remote.origin.fetch='+refs/notes/*:refs/notes/*' git://github.com/freebsd/freebsd.git freebsd.git
$ cd freebsd.git && git pull
$ git log
<We see that revision 243246 is git commit f9ebae3>
$ git checkout f9ebae3
$ cd ../freebsd.svn
$ git --git-dir ../freebsd.git/.git diff
<There should be no output, i.e. no diff>

History

To verify the history and integrity of the conversion, you are advised to run such a conversion yourself and compare (and report) any discrepancies that you find.

• Install the ports devel/subversion, devel/git, devel/qt4-corelib, devel/qmake4

• Get an svnsync clone of the repository you want to verify, the converter can only run against a local copy

• Get the converter and rules: svn co http://svn.freebsd.org/base/user/uqs/git_conv && cd git_conv

• Remove conflicting git configs, these are not for you: rm -rf doc-head.git freebsd-doc.git freebsd-ports.git freebsd-base.git ports-head.git src-head.git

• Build svn2git: cd svn2git/src && make && cd ../..

• Either tweak and run the git_conv script, or do it manually: svn2git/svn-all-fast-export --add-metadata-notes --identity-domain FreeBSD.org --rules freebsd-base.rules /path/to/freebsd-base.svn

• Fetch upstream commits into your repo: cd freebsd-base.git && git remote add origin git://github.com/freebsd/freebsd.git && git fetch origin

• Find out where/if their history diverges: git merge-base master origin/master

To redo this at a later stage, you simply need to

• svnsync sync file:///path/to/freebsd-base.svn

• svn2git/svn-all-fast-export --add-metadata-notes --identity-domain FreeBSD.org --rules freebsd-base.rules /path/to/freebsd-base.svn

• cd freebsd-base.git && git fetch origin

• git merge-base master origin/master

Further Reading

It is *really* recommended, that you read Git for computer scientists and skim GitTalkDevSummit, although it's really outdated.

It really helps to understand the data structure of a git commit, because then you know how merging/rebasing works and can fix snafus easily.

A good visual git reference can be found at A Visual Git Reference.

Implementation Details

The software used for the conversion is a slightly modified fork of svn2git, as used by the KDE project. It can be found at https://gitorious.org/~uqs/svn2git/uqs-svn2git

It requires a rules file to map svn trees and/or revisions to git branches or tags. The current rules don't make use of tags but simply store them as branches.

See the project branch at http://svn.freebsd.org/base/user/uqs/git_conv/ for extra patches, rules and the scripts used to do these conversions.