--R::
- Output diff in reverse. This is useful for displaying output from
- "git-diff-cache" which always compares tree with cache or working
- file. E.g.
-
- git-diff-cache <tree> | git-diff-helper -R file.c
-
- would show a diff to bring the working file back to what
- is in the <tree>.
-
--M::
- Detect renames.