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Andrew Pollock

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Saturday, 11 April 2009

Grappling with Git, episode 1

At work, we have a bit of a vested interest in the Puppet and Facter packages that are in Debian, because we ultimately consume them in Ubuntu.

We noticed that what was in Debian unstable was lagging a bit behind what was released upstream, and when one of my co-workers tried getting in contact with the Debian developers that were maintaining the Puppet package and got no response, I got involved.

I got in touch with Micah Anderson and got myself and Nigel Kersten added to the Alioth project for Puppet.

Despite Jamie Wilkinson being listed as the maintainer of the facter package in Debian, he claimed this was news to him, and Matt Palmer, who was listed as an uploader, didn't really claim much knowledge of maintaining the package either, so we took that as blessing to take over that package as well.

This is where the fun begins.

I've been meaning to try out Git ever since Debconf 7, where all the cool kids were using it and raving about it.

I've been meaning to make the Debian DHCP package collaboratively-maintained, and use Git for the revision control, but I haven't quite gotten off my good intentions and done it yet. Part of the problem is not knowing exactly what workflow I should use, and suffering from paralysis by analysis, reluctant to experiment, because I don't want to go down the wrong path.

Anyway, this is about Puppet, not DHCP. The Puppet package, as it turns out, is already maintained in Git on Alioth, so the problem here was more one of figuring out what the current workflow was, and trying to follow it.

This is where Nigel came in. Conveniently, the upstream Puppet development is done in Git also, and Nigel is a contributor to Puppet upstream, so he had some Git-fu. So between the instructions on how to get started with Git on Alioth and what he knew, we could start fumbling around.

It seems like the Alioth Git repository was also tracking the upstream Puppet repository, as there were commits in the Alioth one by Luke Kanies, and we didn't really imagine that he was doing Debian-specific stuff.

Here's what we ended up doing to try and get what was in the Alioth repository up to the upstream version 0.24.8 of Puppet:

git clone ssh://apollock@git.debian.org/git/pkg-puppet/puppet.git

This part was fairly straight forward. Clone what's in Alioth locally.

git remote add reductive git://reductivelabs.com/puppet
git remote update
git fetch --tags reductive

Next, we added a remote branch that tracked upstream. We called it "reductive", and we updated it. The bit that took some fiddling with was fetching the tags. Nigel later figured out that tags are inherently private to a repository, and normally stay that way. So if I have a local clone of say the upstream Puppet repository, I can tag it to my heart's content, and normally those tags would stay in my local repository, because they're probably only meaningful to me.

git checkout -b upstream/0.24.8 0.24.8

This bit took a bit of work to arrive at as well. What we wanted to do was create a new branch called upstream/0.24.8, which was at what was tagged 0.24.8 in the reductive repository. Nigel pondered what would happen if you already had a tag or a branch called "0.24.8" before you added the remote repository. This is also why we had to fetch the tags from the remote repository, so we had something to check out.

git checkout master
git merge upstream/0.24.8

Next, we switched back to the master branch and merged the contents of our local upstream/0.24.8 branch that we just created. This now got the Puppet source in the master branch up to what was released as version 0.24.8. (and this is better than just running uupdate?)

We did some fiddling with the debian/control file and debian/changelog and fixed up a few things that Lintian was bitching about, and were done.

I'd set up a sid chroot with cowdancer previously, and had to do some faffing around with git-buildpackage to convince it to use pbuilder. I ended up using

git-buildpackage --git-builder="pdebuild --debbuildopts '-i\.git -I.git' -- --basepath /var/cache/pbuilder/base-unstable.cow"

So now we've got most of what we want to ship checked into Git on Alioth. I have no idea if we've done it "right", I suspect we may have done something wrong by operating on the master branch. Looking at the revision history in the Git repository on Alioth, it looks like previously things have been done a few different ways. I certainly want to write up a definitive workflow once we've figured one out.

We haven't uploaded the new package to unstable yet, because we're still trying to give it a modicum of testing, and we'd like to sort out the Facter package as well.

The Facter package was a more greenfield exercise, as while there was already a Git repository on Alioth for it, it was empty. So Nigel had to do some futzing around to get it checked in the right way to make git-buildpackage want to build it. He did this by himself, so I'm not sure exactly what he did. I've since discovered that it's probably lacking some dependencies it needs, so that'll need to get fixed before it gets uploaded.

I look forward to reading blog posts from the smart people who actually know how to use Git properly, telling me how we should have done it.

I'm still very interested in coming up with a proper workflow for preparing packages and committing the changes, and for doing code review.

[18:30] [debian] [permalink]