User name collisions and the git exporter

I was curious about something. I gather the ‘user’ name is used to look up the attribution and email address when doing a git export, and the authors file contains lines like:

user = Some User <user@dom.ain>

So what happens if there are different people at different sites that have the same ‘user’ name, and they each supply patches in (presumably different) commits?

For example, we have a commit by:

bob = Bob Alpha <>

on one system, and:

bob = Bob Omega <>

on another system, and then we want to pull these changes into the master repo?

Does this get more interesting if somebody takes a number of commits and then does a ‘bk collapse’?