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, 1 insertions, 0 deletions

diff --git a/diff.h b/diff.h
index de21f8ecd0..4546aad219 100644
--- a/diff.h
+++ b/diff.h
@@ -60,6 +60,7 @@ struct diff_options {
 		 color_diff_words:1,
 		 has_changes:1,
 		 quiet:1,
+		 no_index:1,
 		 allow_external:1,
 		 exit_with_status:1;
 	int context;