When using the patcher with multiple commits, the messages and author

were getting inappropriately overwritten.
The intent here was to set a default author and message, probably

computed from the review request, as a fallback if any individual patch

did not have its own author or message. Unfortunately, if we decided we

had any patches to process, we'd unconditionally overwrite the metadata

for them instead of only doing it for those which were missing

information.
This was also setting "[x/n] message" for all the patches even when we

were running in squash mode, which meant that if we were applying

multiple patches but squashing to a single commit, the resulting commit

would have the message "[n/n] message" instead of just "message". I've

changed it so if we're expecting to squash (and we have multiple

commits), we always use the default author/message and throw away the

individual commit messages.
This wasn't found when running rbt patch in real life for two reasons:

1. When we do a squash, we are currently only fetch the cumulative diff

   and apply it as a single patch.

2. We currently don't have any cases where commits on the server side

   will be lacking author/message information.
This also fixes up an issue in the patch command where we were using

enumerate when we didn't have to.

Ran unit tests, and fixed up the tests which were now broken.