show --first-parent/-m: do not default to --cc

Given that "git show" always shows some diff and does not walk the history
by default, it is natural to expect "git show --first-parent" to show the
difference between the given commit and its first parent.  It also would
be natural, given that "--cc" is the default, "git show -m" to show
pairwise difference from each of the parents.

We however always defaulted to --cc and there was no way to turn it off.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/builtin-log.c b/builtin-log.c
index ab5f60c9e2..4dd6d2c449 100644
--- a/builtin-log.c
+++ b/builtin-log.c
@@ -329,6 +329,15 @@ static int show_tree_object(const unsigned char *sha1,
 
 static void show_rev_tweak_rev(struct rev_info *rev, struct setup_revision_opt *opt)
 {
+	if (rev->ignore_merges) {
+		/* There was no "-m" on the command line */
+		rev->ignore_merges = 0;
+		if (!rev->first_parent_only && !rev->combine_merges) {
+			/* No "--first-parent", "-c", nor "--cc" */
+			rev->combine_merges = 1;
+			rev->dense_combined_merges = 1;
+		}
+	}
 	if (!rev->diffopt.output_format)
 		rev->diffopt.output_format = DIFF_FORMAT_PATCH;
 }
@@ -347,10 +356,7 @@ int cmd_show(int argc, const char **argv, const char *prefix)
 
 	init_revisions(&rev, prefix);
 	rev.diff = 1;
-	rev.combine_merges = 1;
-	rev.dense_combined_merges = 1;
 	rev.always_show_header = 1;
-	rev.ignore_merges = 0;
 	rev.no_walk = 1;
 	memset(&opt, 0, sizeof(opt));
 	opt.def = "HEAD";