Add a fallback encoding conversion for diff content.
Review Request #3528 — Created Nov. 17, 2012 and submitted
Add a fallback encoding conversion for diff content. When trying to convert the resulting diff content to unicode, we first try straight utf-8, and then try any encodings which were configured on the repository. This change adds one additional step, where we try to interpret the file as utf-8 but replace any unknown characters with U+FFFD.
Ran unit tests.
