[PATCH] Show which files was changed in the git log output

Hi,

I have attached a patch probe to optionally have the git log command
list which files was changed by a commit.

It would be nice if someone with a more in depth knowledge of which
sha1s to pass to diff-tree when there are multiple parents could comment
on whether it does the right thing.

Right now it does the following: if there are only one parent it is
diffed against the commit tree and if there are two parents they are
diffed. I assume the order they are diffed doesn't matter.

-- 
Jonas Fonseca