[PATCH 2/6] diff-merges: move specific diff-index "-m" handling to diff-index

[Sergey Organov <sorganov@gmail.com>]

Move specific handling of "-m" for diff-index to diff-index.c, so
diff-merges is left to handle only diff for merges options.

Being a better design by itself, this is especially essential in
preparation for letting -m imply -p, as "diff-index -m" obviously
should not imply -p, as it's entirely unrelated.

Signed-off-by: Sergey Organov <sorganov@gmail.com>
---
 builtin/diff-index.c | 45 ++++++++++++++++++++++++++++++++++----------
 diff-merges.c        | 13 +------------
 2 files changed, 36 insertions(+), 22 deletions(-)

diff --git a/builtin/diff-index.c b/builtin/diff-index.c
index 176fe7ff2b4e..28bc51d0d8f4 100644
--- a/builtin/diff-index.c
+++ b/builtin/diff-index.c
@@ -12,11 +12,37 @@ static const char diff_cache_usage[] =
 "[<common-diff-options>] <tree-ish> [<path>...]"
 COMMON_DIFF_OPTIONS_HELP;
 
+static int parse_distinct_options(int argc, const char **argv,
+				  struct rev_info *revs, unsigned int *options)
+{
+	int i, left;
+
+	for (i = left = 1; i < argc; i++) {
+		const char *arg = argv[i];
+		int leave = 0;
+
+		if (!strcmp(arg, "--cached"))
+			*options |= DIFF_INDEX_CACHED;
+		else if (!strcmp(arg, "--merge-base"))
+			*options |= DIFF_INDEX_MERGE_BASE;
+		else if (!strcmp(arg, "-m"))
+			revs->match_missing = 1;
+		else
+			leave = 1;
+
+		if (leave)
+			argv[left++] = arg;
+	}
+
+	argv[left] = NULL;
+
+	return left;
+}
+
 int cmd_diff_index(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info rev;
 	unsigned int option = 0;
-	int i;
 	int result;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))
@@ -27,17 +53,16 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	rev.abbrev = 0;
 	prefix = precompose_argv_prefix(argc, argv, prefix);
 
+	/*
+	 * It's essential to parse our distinct options before calling
+	 * setup_revisions(), for the latter not to see "-m".
+	 */
+	argc = parse_distinct_options(argc, argv, &rev, &option);
 	argc = setup_revisions(argc, argv, &rev, NULL);
-	for (i = 1; i < argc; i++) {
-		const char *arg = argv[i];
 
-		if (!strcmp(arg, "--cached"))
-			option |= DIFF_INDEX_CACHED;
-		else if (!strcmp(arg, "--merge-base"))
-			option |= DIFF_INDEX_MERGE_BASE;
-		else
-			usage(diff_cache_usage);
-	}
+	if (argc > 1)
+		usage(diff_cache_usage);
+
 	if (!rev.diffopt.output_format)
 		rev.diffopt.output_format = DIFF_FORMAT_RAW;
 
diff --git a/diff-merges.c b/diff-merges.c
index f3a9daed7e05..4016800c422c 100644
--- a/diff-merges.c
+++ b/diff-merges.c
@@ -30,17 +30,6 @@ static void set_first_parent(struct rev_info *revs)
 	revs->first_parent_merges = 1;
 }
 
-static void set_m(struct rev_info *revs)
-{
-	/*
-	 * To "diff-index", "-m" means "match missing", and to the "log"
-	 * family of commands, it means "show default diff for merges". Set
-	 * both fields appropriately.
-	 */
-	set_to_default(revs);
-	revs->match_missing = 1;
-}
-
 static void set_combined(struct rev_info *revs)
 {
 	suppress(revs);
@@ -108,7 +97,7 @@ int diff_merges_parse_opts(struct rev_info *revs, const char **argv)
 	const char *arg = argv[0];
 
 	if (!strcmp(arg, "-m")) {
-		set_m(revs);
+		set_to_default(revs);
 	} else if (!strcmp(arg, "-c")) {
 		set_combined(revs);
 		revs->combined_imply_patch = 1;
-- 
2.25.1