When using "rbt patch" to apply a change from a review request that was

created with history, it uses the commit message as the message for the

new commit that it's creating. This is ideal when applying a review

request that has multiple commits (since it pulls in all of the messages

for each commit in turn), but it didn't feel right for the simpler case

of applying a change with a single commit. In order to maintain the same

behavior as before, we now use the review request details as the commit

message when there's only one commit.

Verified that after this change, rbt patch -c used the review request

details as the commit message instead of the commit metadata.