Re: [PATCH] Allow git-diff exit with codes similar to diff(1)

"Alex Riesen" [off-list ref] writes:

Challenging... Now, if someone just told me where to look for
differences in diff-tree case...

As the resident git-diff expert I might hack on this myself as
the --quiet options are useful, and --exit-code comes almost
free when you properly do --quiet that implies --quick.

quoted

A slight tangent, but what Linus recalled he thought he did but
he didn't is related to the parts you touched in diff-tree
above.  Because of the interaction with diffcore, these changes
should not be used for the purpose of -exit-code, but catching
the tree level change in the above places and leaving early
would be the right thing to do for comparing the whole tree for
the purpose of simplifying the parents.  Tomorrow will be my git
day so I might whip up a patch to speed that up.

Can it eventually be wired to "-s" (DIFF_FORMAT_NO_OUTPUT)?

I do not think so.  When we run diff internally to pick the set
of paths (i.e. run diffcore and check contents of diff_queue,
just like you did for diff-index/diff-files), we internally use
NO_OUTPUT.  See merge-recursive.c for an example.

quoted

quoted

      diffcore_std(&revs->diffopt);
+     ret = revs->diffopt.diff_exit_code && diff_queued_diff.nr ? 1: 0;
      diff_flush(&revs->diffopt);
      return ret;
 }

This side looks correct, as you are counting queued_diff.nr after
letting diffcore_std() to filter the results.

And it will continue to work if the diffing is left early because of
no output needed. Err, will it?

To implement --quick correctly, you need to know when it is safe
to leave early.  Presence of -S (pickaxe) would most likely mean
you shouldn't leave early.