easy way to demonstrate length of colliding SHA-1 prefixes?

  as part of an upcoming git class i'm delivering, i thought it would
be amusing to demonstrate the maximum length of colliding SHA-1
prefixes in a repository (in my case, i use the linux kernel git repo
for most of my examples).

  is there a way to display the objects in the object database that
clash in the longest object name SHA-1 prefix; i mean, short of
manually listing all object names, running that through cut and sort
and uniq and ... you get the idea.

  is there a cute way to do that? thanks.

rday