The -u option causes 'repo diff' to generate diff output
with file paths relative to the repository root,
so the output can be applied to the Unix 'patch' command.
The name '-u' was selected for convenience, because
both 'diff' and 'git diff' accept the option with the same name
to generate an 'unified diff' output suitable for 'patch' command.
Change-Id: I79c8356db4ed20ecaccc258b3ba139db76666fe0
Reviewed-on: https://gerrit-review.googlesource.com/34380
Reviewed-by: Shawn Pearce <sop@google.com>
Tested-by: Shawn Pearce <sop@google.com>
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