gitosis question: identifying/logging remote user

Hi,

Summary:

I want to be able to log the information that the post-receive hook receives, but I *also* want, along with that, the name of the pubkey that was used in this particular "push".

Detail:

gitosis uses lines in ~git/.ssh/authorized_keys that use ssh's "command=" feature. Specifically, the command is restricted to "gitosis-serve username". Internally, gitosis uses this name to decide if you're allowed to do what you're trying to do.

I'd like it to set an additional env var which will contain "username" so that hooks etc can get that info and use it as they they see fit.

Q1: are there any downsides to doing this?  I don't see any, you're
just creating and setting a new variable but...

Q2: if it's a good idea, can someone give me a hint about where to do
this?  I'm useless at python but I'm willing to try.

Thanks,

Sitaram