Re: [PATCH] diff: alias -q to --quiet

On Fri, Oct 13, 2017 at 09:44:15AM -0700, Anthony Sottile wrote:

I'm not sure if is totally ignored. Normally if we have an unknown options we'd complain:

  $ git diff -x
  error: invalid option: -x

but we don't with "-q". Why?

In builtin/diff.c:471, we can see:

  else if (!strcmp(argv[1], "-q"))
          options |= DIFF_SILENT_ON_REMOVED;

So it _does_ do something, just not what you expected.

But wait, that's not the whole story. We convert "-q" into SILENT_ON_REMOVED in git-diff-files and in git-diff (when we're acting like diff-files). But nobody ever seems to check it!

Running "git log -p -SSILENT_ON_REMOVED" turns up two interesting commits:

  - 95a7c546b0 (diff: deprecate -q option to diff-files, 2013-07-17)

  - c48f6816f0 (diff: remove "diff-files -q" in a version of Git in a
    distant future, 2013-07-18).

So we dropped "-q" a few years ago and added a deprecation notice. "git tag --contains 95a7c546b0" tells us that happened in v1.8.5, which shipped in Nov 2013.

And then in v2.0.0 (May 2014) we tried to drop "-q" completely. Looking over c48f6816f0, I _think_ it's a mistake that "-q" became a silent noop there. That commit should have ripped out the remaining bits that set the SILENT_ON_REMOVED flag, and "-q" would have become an error.

So there are two separate questions/tasks:

  1. Should we remove the special handling of "-q" leftover from this
     deprecation? I think the answer is yes.

  2. Should we teach the diff machinery as a whole to treat "-q" as a
     synonym for "--quiet".

     Probably yes, but it's less clear to me that this won't have funny
     interactions. Are there other commands which use the diff-options
     parser via setup_revisions(), but expect "-q" to be left in the
     output so that they can handle it themselves?

     It looks like git-log does so, but it pulls the "-q" out before
     handing the remainder to setup_revisions(). And anyway, it just
     converts the option into a quiet diff (though it does in a way
     that's different than the rest of the diff code -- that might bear
     investigating on its own).

     Grepping for 'q' and OPT__QUIET, I don't see any others, but I
     didn't spend very much time digging.

-Peff