The move to git!

Jesse Keating jkeating at
Fri Jul 30 03:55:09 UTC 2010

Hash: SHA1

This evening we opened up dist-git for business.  Dist-git is our git
based replacement for dist-cvs, the source control system we were using
for our package specs, patches, and source files.  This has been a long
time coming and a massive effort.  I want to take a little time here to
outline what we've done and where we are going.

First a brief outline of how our CVS system worked.  CVS is a daemon of
sorts, and all repos typically live within a single CVSROOT.  Within
this CVSROOT we had an 'avail' system to make use of, that we could
populate with data from Fedora Account System and dump into this file.
Avail worked on path names, relative to the CVSROOT.  Since we used
directories for each Fedora release as pseudo branches we could set
avail info on each release "branch".  CVS also used some filesystem
symlink tricks to create a "common" subdir for every package module, and
this is where we stuffed common scripts and Makefile content.  Pretty
clever on one hand, we can make updates to the make system without
touching every single package, but it is pretty hackish and we had
constant issues where somebody would attempt an action using old common
content and stuff would fall over.

Now we look at git.  Git is for the most part a daemonless system.  Each
repository is completely stand alone and generally does not require any
other infrastructure to be useful.  You can interact with a repository
directly on the filesystem using /usr/bin/git or you can interact with
it through say ssh, again using /usr/bin/git (your local /usr/bin/git
will call a remote /usr/bin/git).  Generally there is no running daemon
to connect to and authenticate with.  Basic authentication of who can
check out what and commit where with git happens at the filesystem
permissions level.  One twist with this is that with git, we wanted to
use real branches within a package repo to reflect the different
Fedora/EPEL releases.  In repo branches are not reflected with path
names that we could set filesystem ACLs upon, so this posed a problem
for our conversion.

Enter gitolite.  Gitolite ( )is an
addon system to git that provides ACL functionality including different
rights for different branches within a given repository, and more!  By
using gitolite as a replacement for /usr/bin/git when a user connects to
our git server we can again utilize the information we have within the
Fedora Package Database and properly allow / restrict changes on
specific branches for specific developers.  The gitolite upstream (
Sitaram Chamarty, sitaram at ) has been fantastically
responsive to our needs, which are admittedly a little unique.  We have
a very large set of repositories (over 10.5K) and a largish number of
contributors (1050).  The combination of the two leads to a very very
large and complex ACL structure that at first broke the system quite
badly.  Upstream was very quick to create a "bigconfig" method of
compiling the ACLs without crashing the box.  Our other unique needs
involve having individual accounts for each committer instead of a
shared account with a large list of allowed SSH keys.  Add to that some
of our accounts need to be able to ssh shell into the git server for
administrative duties.  Throughout our trials and testing with gitolite
every time we've ran into some issue that just didn't fit the mold,
Sitaram has been there with a smile and a fix.  At this point our
production server is a whopping one line different from current gitolite
upstream.  This is a fantastic win for us, for our sustainability, and
for the next large group that wants to make use of gitolite.

Once we had a plan for ACLs and for branches, we had to decide if we
were going to replace the Make system and with what.  I had never been a
fan of Make, it was entirely too difficult to modify and innovate with.
 Since I was the one pushing this transition forward, I decided to write
a new tool in my favorite language, python.  The fedpkg tool was born
and took off.  fedpkg was born around January 4th, 2010 and has since
grown into 1,523 (via sloccount) lines of code.  While far from
complete, it is a great start (if I do say so myself!) at replacing the
make system.  Because it is written in python (or maybe just !Make) it
seems to be easier to contribute to, and I've already gotten a number of
contributions.  More will come as it starts to be more widely used.  The
biggest challenge with fedpkg is removing the need to update something
on the end user's system every single time we added a new Fedora release
and changed what happens when you build for rawhide.  I'll spare you the
details but I'm fairly happy with what we have.  The end result should
be far fewer misfires and end user confusion.

The last major piece of the puzzle was how to actually convert the
existing CVS repositories, including the fun pseudo branches, into git
repositories.  I tried a number of options over the years (I've been
working on this off and on for nearly 4 years!) ranging from the built
in git cvsimport to git-svn to parsecvs and a few others.  In the end,
we took a page from the gnome project and used parsecvs ( ) for the vast majority of
our repositories.  There were a few that gave parsecvs fits and recent
versions of git cvsimport were able to handle them.  The git system is
fantastic enough that we were able to merge our pseudo cvs branches into
actual git branches complete with a real shared history, but again I'll
spare you the details of the scripting to do this.  All but the kernel
repo  seems to have converted successfully which is a pretty good
success rate in my book.  We may yet get the kernel converted, but in
the interest of time we opted to start fresh with dist-git for now.

Without the help of many others, this project would never have gotten
done.  Folks helped out with Koji modifications, with fedpkg
contributions, with repeated testing of attempted conversions, with
logic checking of my plans, of helping me understand more of git
internals and deciphering error output, and most of all with being
patient while we worked through the transition and very positive along
the way.  Things will be bumpy over the next few weeks as we really
start putting distgit to the test.  No amount of staging and testing can
really replace production use.  There will be many more updates to
fedpkg as bugs are found and fixed and features are contributed.  Wiki
pages will get filled out as knowledge of how to interact with dist-git
starts to spread ( is a
good start ).

Once again I want to thank everybody who helped out and for all the
(continued) patience!  I'll be available via email and IRC as much as
possible the next few days to help anybody with dist-git issues.  Look
for Oxf13 on freenode.  Happy gitting!

- -- 
Jesse Keating
Fedora -- Freedom² is a feature!
Version: GnuPG v2.0.14 (GNU/Linux)
Comment: Using GnuPG with Fedora -


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