[MERGE] Add a smart method method that can pull a set of revisions in a single request

[Aaron Bentley]

Aaron Bentley has voted resubmit.
Status is now: Resubmit
Comment:
I believe this will introduce regressions when pulling from repositories 
with broken last-modified data, because it doesn't emulate 
iter_file_revisions_aggressive.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C20070814082312.GL25450%40steerpike.home.puzzling.org%3E