parse-options: make OPT_ARGUMENT() more useful

`OPT_ARGUMENT()` is intended to keep the specified long option in `argv`
and not to do anything else.

However, it would make a lot of sense for the caller to know whether
this option was seen at all or not. For example, we want to teach `git
difftool` to work outside of any Git worktree, but only when
`--no-index` was specified.

Note: nothing in Git uses OPT_ARGUMENT(). Even worse, looking through
the commit history, one can easily see that nothing even
ever used it, apart from the regression test.

So not only do we make `OPT_ARGUMENT()` more useful, we are also about
to introduce its first real user!

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/parse-options.c b/parse-options.c
index cec74522e5..1d57802da0 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -286,6 +286,8 @@ again:
 					     optname(options, flags));
 			if (*rest)
 				continue;
+			if (options->value)
+				*(int *)options->value = options->defval;
 			p->out[p->cpidx++] = arg - 2;
 			return PARSE_OPT_DONE;
 		}