Feature Request: commits where $LOCAL and $REMOTE are from

[Joshua Hudson <jhudson@xxxxxxxxxxx>]

We got ourselves in a bit of a pickle. We are trying to write a custom 
diff/merge tool for some of our files in source control, but to display 
a readable diff, we need to read other files, that may or may not have 
changed.

We think we can solve this problem with two more variables in the 
command line that tell us which commit hash to fetch the additional 
files from (yes, it can be the working tree; we'd like to know if it is).