Is there any way to delete old commits?

[Jonathan Dieter <jdieter lesbg com>]

I'm the system administrator for a school in Beirut that has over 100 
seats running Fedora.  Currently we're using kickstarts for initial 
install, ansible for configuration, and some fancy footwork with offline 
updates to make sure the systems get upgraded on shutdown.  With all 
this, we have issues with systems getting restarted while updating and 
other strange things.

I'd really like to start using OSTree to make sure we're using 
consistent images and I've managed to get a perfect image set up, but 
I've run into a stumbling block.  Our image runs at somewhere between 
15GB - 20GB.  If I push out an updated image once a week or so, there 
will come a point in the not so distant future where the history is 
ridiculously large.

Is there any way to trim the history on our tree so that we discard any 
commits beyond the last few?  Is this even a reasonable thing to ask?

Thanks,
Jonathan