caching commit patch-ids for fast git-cherry

I'm planning to use cherry picking to manage long term syncing between cvs/perforce and git repositories. This means I'll have scripts running git-cherry between branches with hundreds of uncommon commits, and I want git-cherry to be much, much, faster.

It looks like I can do this by caching commit->patch-id pairs from
commit_patch_id() in patch-ids.c to a file, say
$GIT_DIR/commit-patch-id-cache.  The file would be binary and append
only, and could be blown away if .  Any suggestions / concerns before
I write this?  Is there any reusable efficient map code for storing
the commit->patch-id map, or should I just mirror the blocked storage
+ binary search used for struct patch_ids?

Thanks, Geoffrey