Extra metadata in the commit?

[Scott Chacon <schacon@gmail.com>]

Hey all,

I'm working on a hg<->git bidirectional tool using Git as the
communication protocol, so there is a bunch of Hg metadata that I need
to keep in Git to ensure I can convert commits created in Hg back into
the exact same objects after they upload to the Git db and then come
back down.  This means storing explicit rename info, branch names, etc
somewhere without messing up Git clients that want to work on the same
repo.  So, I can keep this data in the commit message, but I thought
it would be cleaner to keep it as extra fields in the commit object
before the "\n\n" separator.  Before I go too far down this road, is
there anything horrible that might happen in any of the core Git tools
if extra data is there?

Thanks,
Scott