[PATCH v2 3/4] builtin/diff: parse --no-index using parse_options()

[Denton Liu <liu.denton@gmail.com>]

Instead of parsing the `--no-index` option with a plain strcmp, use
parse_options() to parse options. This allows us to easily add more
options in a future commit.

As a result of this change, `--no-index` is removed from `argv` so, as a
result, we no longer need to handle it in diff_no_index().

Signed-off-by: Denton Liu <liu.denton@gmail.com>
---
 builtin/diff.c  | 33 ++++++++++++++++++++++-----------
 diff-no-index.c | 15 +++------------
 2 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/builtin/diff.c b/builtin/diff.c
index cb98811c21..0e086ed7c4 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -373,6 +373,13 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	int nongit = 0, no_index = 0;
 	int result = 0;
 	struct symdiff sdiff;
+	struct option options[] = {
+		OPT_SET_INT_F(0, "no-index", &no_index,
+			   N_("compare the given paths on the filesystem"),
+			   DIFF_NO_INDEX_EXPLICIT,
+			   PARSE_OPT_NONEG),
+		OPT_END(),
+	};
 
 	/*
 	 * We could get N tree-ish in the rev.pending_objects list.
@@ -406,21 +413,25 @@ int cmd_diff(int argc, const char **argv, const char *prefix)
 	 * Other cases are errors.
 	 */
 
-	/* Were we asked to do --no-index explicitly? */
-	for (i = 1; i < argc; i++) {
-		if (!strcmp(argv[i], "--")) {
-			i++;
-			break;
-		}
-		if (!strcmp(argv[i], "--no-index"))
-			no_index = DIFF_NO_INDEX_EXPLICIT;
-		if (argv[i][0] != '-')
-			break;
-	}
+	argc = parse_options(argc, argv, prefix, options, NULL,
+			     PARSE_OPT_KEEP_DASHDASH |
+			     PARSE_OPT_KEEP_ARGV0 |
+			     PARSE_OPT_KEEP_UNKNOWN |
+			     PARSE_OPT_NO_INTERNAL_HELP);
 
 	prefix = setup_git_directory_gently(&nongit);
 
 	if (!no_index) {
+		int i;
+		for (i = 1; i < argc; i++) {
+			if (!strcmp(argv[i], "--")) {
+				i++;
+				break;
+			}
+			if (argv[i][0] != '-')
+				break;
+		}
+
 		/*
 		 * Treat git diff with at least one path outside of the
 		 * repo the same as if the command would have been executed
diff --git a/diff-no-index.c b/diff-no-index.c
index 7814eabfe0..da82e2d090 100644
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -243,28 +243,19 @@ int diff_no_index(struct rev_info *revs,
 		  int implicit_no_index,
 		  int argc, const char **argv)
 {
-	int i, no_index;
+	int i;
 	const char *paths[2];
 	struct strbuf replacement = STRBUF_INIT;
 	const char *prefix = revs->prefix;
-	struct option no_index_options[] = {
-		OPT_BOOL_F(0, "no-index", &no_index, "",
-			   PARSE_OPT_NONEG | PARSE_OPT_HIDDEN),
-		OPT_END(),
-	};
-	struct option *options;
 
-	options = parse_options_concat(no_index_options,
-				       revs->diffopt.parseopts);
-	argc = parse_options(argc, argv, revs->prefix, options,
+	argc = parse_options(argc, argv, revs->prefix, revs->diffopt.parseopts,
 			     diff_no_index_usage, 0);
 	if (argc != 2) {
 		if (implicit_no_index)
 			warning(_("Not a git repository. Use --no-index to "
 				  "compare two paths outside a working tree"));
-		usage_with_options(diff_no_index_usage, options);
+		usage_with_options(diff_no_index_usage, revs->diffopt.parseopts);
 	}
-	FREE_AND_NULL(options);
 	for (i = 0; i < 2; i++) {
 		const char *p = argv[argc - 2 + i];
 		if (!strcmp(p, "-"))
-- 
2.28.0.618.gf4bc123cb7