git log command supports a
--grep flag that allows you to do a text
search (using grep, obviously) over the commit messages for that repository.
For the git user that writes descriptive commit messages, this can come in
quite handy. In particular, this can be put to use in an environment where
the standard process involves including ticket and bug numbers in the commit
message. For example, finding bug
#123 can be accomplished with:
$ git log --grep="#123"
man git-log for more details.