cherry picking changesets instead of commits

I have a project stored in a git repository with other versions stored in both cvs and perforce (sadly). I want the ability to propagate changes back and forth between all three repositories without mangling the git history. I specifically want to avoid (1) having two copies of each commit (e.g., an initial version and a version pulled from cvsimport) and (2) commits full of git-p4 metadata (the [git-p4] lines in commit messages).

One way to do this would be to have cvs branch imported using "git cvsimport", and a perforce branch imported via "git-p4", and communicate between the cvs/p4 branches and the main git branches entirely through cherry picking. Unfortunately, "git cherry" doesn't recognize when commits with potentially different author names or log messages polluted with "[git-p4]" produce the same changeset, so if I export a change from the git master branch through cvsexportcommit and update the cvs branch with cvsimport, "git cherry" will report that the change doesn't exist on the git master branch.

Has anyone tackled this problem before? Would it be straightforward to add an option to "git cherry" to ignore differences in metadata? The cherry documentation doesn't give its criteria for when commits match, and I'm not familiar enough with the code yet to figure out those criteria directly from cmd_cherry in builtin-log.c.

Thanks, Geoffrey