Sunday, April 22, 2007

Switching version control systems

We have been using GNU arch the last couple of years as a version control system, however Tom Lords' implementation does not scale well, and some of our software packages have 10 thousands of commits. This means that a single commit operation may take _minutes_. It is awful to wait so much time for a single commit, and it really degrades productivity.

I was considering Mercurial, Bazaar-NG and git, however this was not an easy decision, as the "modern" version control systems promote the use of branches over anything else, and our current version control model relied on cherry-picking heavily:
  • developer commits the solution for each bug separately to his/her branch
  • QA people pick patches from developer branches and integrate them to a 'test' branch, once the test was successful,
  • release manager picks patches from the 'test' branch and integrates to mainline, if he doesn't find anything odd during review
This worked wonderfully in GNU arch, but new VC systems lack in this area. Bazaar has no cherry picking support at all, Mercurial has some incomplete support with a plugin named transplant, git has cherry picking, but that relies on heuristics (it guesses whether a patch was integrated by using a checksum of the patch).

I was considering to change the process I outlined above, but I'm not sure how that would work out. We sometimes need to work with people not really experienced with VC systems at all, asking them to manage their own branches for each bugfix/problem group seems to raise the bar a bit too high.

Nevertheless git seemed to have solutions for both worlds (e.g. picking patches AND merging branches), so I choose git over the other two, and now I converted some of the syslog-ng history to git in order to gather some real-life experience.

I like what I see so far, git 1.5.x is really way better than older versions on the usability and documentation front. I now feel comfortable enough with git as I could finally understand the working model and the structure of the git history.And git is fast like lightning :)

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