Retroactively change email signature?

Hi,

I imagine that changing old commits is considered one of the great evils of source control, but I have a small problem: I have a habit of testing my code on several different computers and operating systems. Sometimes when setting up a new computer for testing (and thus, for development, since testing always results in a few commits), I have forgotten to use git-config to configure my name and email address.

Since git doesn't warn when I've forgotten to do this, my git-log is now sprinkled with various email addresses, some which are just my username@hostname. This is completely useless to people who might view my public repository.

Is it possible to retroactively change the author and email of several commits? Perhaps some sort of search-and-replace for the commit metadata? Even for older commits, I'd like to change the email addresses to my current address.

If it's not possible it's not the end of the world, but I thought it wouldn't hurt to ask.

thanks, Steve