When either the old or new file contents have no newline at the end of
the file, then git-diff(1) will print out a "\ No newline at end of
file" indicator. While we do correctly handle this in the case where the
new file has this indcator, we fail to parse patches where the old file
is missing a newline at EOF.

Fix this bug by handling and missing newline indicators in the old file.
Add tests to verify that we can parse such files.