diff-merges: do not imply -p for new options

Add 'combined_imply_patch' field and set it only for old --cc/-c
options, then imply -p if this flag is set instead of implying -p
whenever 'combined_merge' flag is set.

We don't want new --diff-merge options to imply -p, to make it
possible to enable output of diffs for merges independently from
non-merge commits. At the same time we want to preserve behavior of
old --c/-c/-m options and their interactions with --first-parent, to
stay backward-compatible.

This patch is first step in this direction: it separates old "--cc/-c
imply -p" logic from the rest of the options.

Signed-off-by: Sergey Organov <sorganov@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff-merges.c

@@ -9,6 +9,7 @@ static void suppress(struct rev_info *revs)
 	revs->combine_merges = 0;
 	revs->dense_combined_merges = 0;
 	revs->combined_all_paths = 0;
+	revs->combined_imply_patch = 0;
 }
 
 static void set_separate(struct rev_info *revs)
@@ -74,19 +75,21 @@ int diff_merges_parse_opts(struct rev_info *revs, const char **argv)
 	const char *optarg;
 	const char *arg = argv[0];
 
-	if (!strcmp(arg, "-m"))
+	if (!strcmp(arg, "-m")) {
 		set_m(revs);
-	else if (!strcmp(arg, "-c"))
+	} else if (!strcmp(arg, "-c")) {
 		set_combined(revs);
-	else if (!strcmp(arg, "--cc"))
+		revs->combined_imply_patch = 1;
+	} else if (!strcmp(arg, "--cc")) {
 		set_dense_combined(revs);
-	else if (!strcmp(arg, "--no-diff-merges"))
+		revs->combined_imply_patch = 1;
+	} else if (!strcmp(arg, "--no-diff-merges")) {
 		suppress(revs);
-	else if (!strcmp(arg, "--combined-all-paths"))
+	} else if (!strcmp(arg, "--combined-all-paths")) {
 		revs->combined_all_paths = 1;
-	else if ((argcount = parse_long_opt("diff-merges", argv, &optarg)))
+	} else if ((argcount = parse_long_opt("diff-merges", argv, &optarg))) {
 		set_diff_merges(revs, optarg);
-	else
+	} else
 		return 0;
 
 	revs->explicit_diff_merges = 1;
@@ -126,8 +129,9 @@ void diff_merges_setup_revs(struct rev_info *revs)
 		revs->first_parent_merges = 0;
 	if (revs->combined_all_paths && !revs->combine_merges)
 		die("--combined-all-paths makes no sense without -c or --cc");
-	if (revs->combine_merges) {
+	if (revs->combine_merges)
 		revs->diff = 1;
+	if (revs->combined_imply_patch) {
 		/* Turn --cc/-c into -p --cc/-c when -p was not given */
 		if (!revs->diffopt.output_format)
 			revs->diffopt.output_format = DIFF_FORMAT_PATCH;

revision.h

@@ -197,6 +197,7 @@ struct rev_info {
 			separate_merges: 1,
 			combine_merges:1,
 			combined_all_paths:1,
+			combined_imply_patch:1,
 			dense_combined_merges:1,
 			first_parent_merges:1;