git-statplotto dump out object counts and sizes by earliest date entered. Plotting these with Gnuplot gave me some interesting results:
The git.git repository (red line) appears to have a very stable history, but sees a huge spike right around now. This spike is an outlier caused by my development repository; I was very actively rebasing a branch on Feb 26th, resulting in hundreds of commits in my reflog.
The linux-2.6.git history seems to show a periodic cycle, with some days reaching up to 700 commits per day. The obvious correlation between number of KiB of disk space used and the number of commits per day is also clearly visible. As I am not a kernel developer the linux-2.6.git data came from a mirror of Linus' repository. I ommitted the first day outlier to prevent the Y-axis scales from shooting through the roof.
I have linked the images to higher-resolution PDFs, clicking on them will give you the PDFs.