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HOWTO: use Gource with Perforce

You may have heard of Gource, the source code control visualization gadget. It’s a utility that creates an animation of the activity in your source control system, giving a unique view of the life of a project over time. I finally got some time to play around with it a couple weeks ago, and I used it to make a video of the development activity on ElectricAccelerator over the past 9 years. The “full length” version is about 30 minutes long and plays on a loop in the breakroom at the office, but here’s a shorter, anonymized version (I recommend putting this or this in the background to provide a soundtrack for the animation):

I don’t think it’s necessarily very useful, but there’s no denying that it’s enthralling to watch, especially when it represents your own project. This visualization does really drive home one thing though: just how active development on ElectricAccelerator is, even now, after 9 years. I used to think that we would be “done” at some point, maybe a few years after we started. Now I think we may never be — in fact, I hope we aren’t!

Integrating Gource and Perforce

Gource is what I call “falling over easy” to use. At least, it is if you’re using one of the source control systems it supports natively. Unfortunately, Gource doesn’t directly support Perforce, our source control system, so to make the video above, I had to convert our Perforce commit logs to a format Gource could handle. That’s not too hard to do actually, and in fact several people have written scripts to do it.

Only trouble is, those adapters don’t handle big projects with many branches very well. Instead, they seem to be designed to handle simple projects with one or a few branches, or to enable visualization of just one of the many branches in your project. Either way, that doesn’t work for us. We’ve got about 30 branches in the Accelerator depot, since we make a new branch for each release, as well as for specific large features that we expect will take a long time to complete, so we can’t simply show all the branches. And if we show just one branch, such as our main branch, the trunk of the tree, the visualization will tend to significantly over-represent my contributions, because I handle most of the cross-branch merges.

So I wrote my own adapter: p42gource.tcl. The key differences in this adapter compared to others are that it incorporates activity from as many branches as you specify; and it ignores branch and integrate operations, since those are merely echoes of “interesting” operations on other branches.

Now, getting from Perforce commit logs to Gource is simple (NB: before using p42gource.tcl, you have to edit it to add the list of branches you want to include in the conversion):

$ # Get the id of the last submitted changelist
$ p4 changes -s submitted -m 1 | awk '{print $2}'
50594
$ # Get the details for each changelist
$ for n in {1..50594} ; do p4 describe -s $n >> p4.log ; done
$ # Create a Gource-style log from the Perforce data
$ tclsh p42gource.tcl < p4.log > gource.log
$ # Run Gource
$ gource --log-format custom gource.log

Give it a try!

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