diff-merges: cleanup set_diff_merges()

Get rid of special-casing of 'suppress' in set_diff_merges(). Instead
set 'merges_need_diff' flag correctly in every option handling
function.

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

diff-merges.c

@@ -20,9 +20,20 @@ static void suppress(struct rev_info *revs)
 	revs->remerge_diff = 0;
 }
 
-static void set_separate(struct rev_info *revs)
+static void common_setup(struct rev_info *revs)
 {
 	suppress(revs);
+	revs->merges_need_diff = 1;
+}
+
+static void set_none(struct rev_info *revs)
+{
+	suppress(revs);
+}
+
+static void set_separate(struct rev_info *revs)
+{
+	common_setup(revs);
 	revs->separate_merges = 1;
 	revs->simplify_history = 0;
 }
@@ -35,21 +46,21 @@ static void set_first_parent(struct rev_info *revs)
 
 static void set_combined(struct rev_info *revs)
 {
-	suppress(revs);
+	common_setup(revs);
 	revs->combine_merges = 1;
 	revs->dense_combined_merges = 0;
 }
 
 static void set_dense_combined(struct rev_info *revs)
 {
-	suppress(revs);
+	common_setup(revs);
 	revs->combine_merges = 1;
 	revs->dense_combined_merges = 1;
 }
 
 static void set_remerge_diff(struct rev_info *revs)
 {
-	suppress(revs);
+	common_setup(revs);
 	revs->remerge_diff = 1;
 	revs->simplify_history = 0;
 }
@@ -57,7 +68,7 @@ static void set_remerge_diff(struct rev_info *revs)
 static diff_merges_setup_func_t func_by_opt(const char *optarg)
 {
 	if (!strcmp(optarg, "off") || !strcmp(optarg, "none"))
-		return suppress;
+		return set_none;
 	if (!strcmp(optarg, "1") || !strcmp(optarg, "first-parent"))
 		return set_first_parent;
 	if (!strcmp(optarg, "separate"))
@@ -81,10 +92,6 @@ static void set_diff_merges(struct rev_info *revs, const char *optarg)
 		die(_("invalid value for '%s': '%s'"), "--diff-merges", optarg);
 
 	func(revs);
-
-	/* NOTE: the merges_need_diff flag is cleared by func() call */
-	if (func != suppress)
-		revs->merges_need_diff = 1;
 }
 
 /*
@@ -115,6 +122,7 @@ int diff_merges_parse_opts(struct rev_info *revs, const char **argv)
 
 	if (!suppress_m_parsing && !strcmp(arg, "-m")) {
 		set_to_default(revs);
+		revs->merges_need_diff = 0;
 	} else if (!strcmp(arg, "-c")) {
 		set_combined(revs);
 		revs->merges_imply_patch = 1;
@@ -125,7 +133,7 @@ int diff_merges_parse_opts(struct rev_info *revs, const char **argv)
 		set_remerge_diff(revs);
 		revs->merges_imply_patch = 1;
 	} else if (!strcmp(arg, "--no-diff-merges")) {
-		suppress(revs);
+		set_none(revs);
 	} else if (!strcmp(arg, "--combined-all-paths")) {
 		revs->combined_all_paths = 1;
 	} else if ((argcount = parse_long_opt("diff-merges", argv, &optarg))) {
@@ -139,7 +147,7 @@ int diff_merges_parse_opts(struct rev_info *revs, const char **argv)
 
 void diff_merges_suppress(struct rev_info *revs)
 {
-	suppress(revs);
+	set_none(revs);
 }
 
 void diff_merges_default_to_first_parent(struct rev_info *revs)