WordPress MU

Is there a code repository that NON MU developers can view the MU code with revisions? I tried automattic and it requires authentication.

I want to see the history of a specific file in the tree.

You mean trac?

http://trac.mu.wordpress.org/

1) General changes

2) A more specific timeline from TRAC

3) Again with TRAC, you can browse the tree, view a file, then "View Changes" (diff) between specific ticket numbers...

The last one is probably what you're looking for...