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.

CAVEAT EMPTOR: It is possible (but highly unlikely) that the repositories might need to be re-done due to bugs in the converter. This would result in changed commit IDs for the impacted branches. As the actual tree objects for a certain SVN revision will remain identical, it will always be possible to rebase or merge your work on these new branches and not run into any merge conflicts. Advance notice will be provided if this proves necessary, along with advice on the required git commands.

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).

Known Problems

Quick Start

$ git clone --config remote.origin.fetch='+refs/notes/*:refs/notes/*' https://github.com/YourGitUserName/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.

Adding SVN Revision Notes to an Existing Clone

The git notes in the Github repositories contain useful information, and show up in git-log if present. git-clone without the --config ... line from above will default to not cloning refs/notes. You can configure the local git repo to fetch notes like so:

$ cd freebsd
$ git config --add remote.origin.fetch '+refs/notes/*:refs/notes/*'
$ git fetch   # It's many MB for src, will take some time

It will add lines to your git log output like this:

Notes:
    svn path=/head/; revision=277815

Integration

Using git-svn

Using git-svn

Merging pull requests from github using git-svn (FreeBSD committers only)

Merging pull requests from GitHub

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/idaemons/freebsd and follow the instructions described in the README file.

FAQ

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/*' https://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.

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

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.

This is a decent book on getting started with Git ($16 USD for ebook) Pragmatic Guide to Git

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.

GitWorkflow (last edited 2015-04-27 18:39:13 by CraigRodrigues)