When looking up review requests for a commit, we'd attempt to find one

that has a matching commit_id field if the commit description didn't

explicitly specify an ID. However, this lookup did not take the

repository into account, resulting in problems if two review requests

across two different repositories had the same commit ID.
This is not a major problem for Git and Mercurial. In theory, it could

affect Subversion on Google Code, but we actually have that matching

disabled (though we likely suffered from another bug as a result).
The repository is now passed to the matcher function, and is required

for commit ID matching.

Unit tests pass.