diff: squelch empty diffs even more

When we compare two non-tracked files, or explicitly
specify --no-index, the suggestion to run git-status
is not helpful.

The patch adds a new diff_options bitfield member, no_index, that
is used instead of the special value of -2 of the rev_info field
max_count to indicate that the index is not to be used.  This makes
it possible to pass that flag down to diffcore_skip_stat_unmatch(),
which only has one diff_options parameter.

This could even become a cleanup if we removed all assignments of
max_count to a value of -2 (viz. replacement of a magic value with
a self-documenting field name) but I didn't dare to do that so late
in the rc game..

The no_index bit, if set, then tells diffcore_skip_stat_unmatch()
to not account for any skipped stat-mismatches, which avoids the
suggestion to run git-status.

Signed-off-by: Rene Scharfe <rene.scharfe@lsfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/diff.c b/diff.c
index f884de77a..97cc5bc08 100644
--- a/diff.c
+++ b/diff.c
@@ -3185,7 +3185,8 @@ static void diffcore_skip_stat_unmatch(struct diff_options *diffopt)
 			 * to determine how many paths were dirty only
 			 * due to stat info mismatch.
 			 */
-			diffopt->skip_stat_unmatch++;
+			if (!diffopt->no_index)
+				diffopt->skip_stat_unmatch++;
 			diff_free_filepair(p);
 		}
 	}