Re: git-diff: must --exit-code work with --ignore* options?

Junio C Hamano wrote:

Jim Meyering [off-list ref] writes:

quoted

git-diff's --quiet option works how I'd expect with --ignore-space-at-eol
as long as I'm also using --no-index:

    $ echo>b; echo \ >c; git diff --no-index --quiet --ignore-space-at-eol b c \
      && echo good
    good

But in what I think of as normal operation (i.e., without --no-index),
--exit-code (or --quiet) makes git-diff say there were differences,
even when they have been ignored:

    # do this in an empty directory
    $ git init -q; echo>k; git add .; git commit -q -m. .; echo \ >k
    $ git diff --ignore-space-at-eol --quiet || echo bad
    bad

I am slightly torn about this, in that I can picture myself saying that
this is unintuitive on some different days, but not today ;-)

Thanks for the quick reply.  Here's why I noticed:

I wanted to ensure that the only changes induced by commit C were
to trailing blanks.  I wrote something like this, expecting to be able
to deal with the exception:

    git --quiet --ignore-space-at-eol --quiet C^..C || handle_unexpected

But handle_unexpected was always being invoked.
I was surprised because GNU diff's --ignore-all-space (-w) option does
work the way I expected:

    $ echo>b; echo \ >c; diff -w b c && echo $?
    0

If you look at the output (i.e. no --quiet), you would see that the blob
changes are still reported for the path.  E.g.  you would see something
like...

	$ git diff --ignore-space-at-eol
        diff --git a/k b/k
        index 8b13789..8d1c8b6 100644

The "index" line is still showing that there _is_ a difference.

I did see that, to my chagrin:
if using a --ignore-... option had also suppressed those, I could
have tested for empty output instead of exit status.

The --ignore-* options are there merely to tell git what changes are not
worth _showing_ in the textual part of the patch, in order to cut down the
amount of the output.  It never affects the outcome.

So if anything, I think --no-index codepath is what's buggy; if it does
not report the blob difference that is a different matter, though.

If need be, I can work around it.