diff-lib: accept option flags in run_diff_index()

In a future commit, we will teach run_diff_index() to accept more
options via flag bits. For now, change `cached` into a flag in the
`option` bitfield. The behaviour should remain exactly the same.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/diff-index.c

@@ -15,7 +15,7 @@ COMMON_DIFF_OPTIONS_HELP;
 int cmd_diff_index(int argc, const char **argv, const char *prefix)
 {
 	struct rev_info rev;
-	int cached = 0;
+	unsigned int option = 0;
 	int i;
 	int result;
 
@@ -32,7 +32,7 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 		const char *arg = argv[i];
 
 		if (!strcmp(arg, "--cached"))
-			cached = 1;
+			option |= DIFF_INDEX_CACHED;
 		else
 			usage(diff_cache_usage);
 	}
@@ -46,7 +46,7 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 	if (rev.pending.nr != 1 ||
 	    rev.max_count != -1 || rev.min_age != -1 || rev.max_age != -1)
 		usage(diff_cache_usage);
-	if (!cached) {
+	if (!(option & DIFF_INDEX_CACHED)) {
 		setup_work_tree();
 		if (read_cache_preload(&rev.diffopt.pathspec) < 0) {
 			perror("read_cache_preload");
@@ -56,7 +56,7 @@ int cmd_diff_index(int argc, const char **argv, const char *prefix)
 		perror("read_cache");
 		return -1;
 	}
-	result = run_diff_index(&rev, cached);
+	result = run_diff_index(&rev, option);
 	UNLEAK(rev);
 	return diff_result_code(&rev.diffopt, result);
 }

builtin/diff.c

@@ -134,11 +134,11 @@ static int builtin_diff_blobs(struct rev_info *revs,
 static int builtin_diff_index(struct rev_info *revs,
 			      int argc, const char **argv)
 {
-	int cached = 0;
+	unsigned int option = 0;
 	while (1 < argc) {
 		const char *arg = argv[1];
 		if (!strcmp(arg, "--cached") || !strcmp(arg, "--staged"))
-			cached = 1;
+			option |= DIFF_INDEX_CACHED;
 		else
 			usage(builtin_diff_usage);
 		argv++; argc--;
@@ -151,7 +151,7 @@ static int builtin_diff_index(struct rev_info *revs,
 	    revs->max_count != -1 || revs->min_age != -1 ||
 	    revs->max_age != -1)
 		usage(builtin_diff_usage);
-	if (!cached) {
+	if (!(option & DIFF_INDEX_CACHED)) {
 		setup_work_tree();
 		if (read_cache_preload(&revs->diffopt.pathspec) < 0) {
 			perror("read_cache_preload");
@@ -161,7 +161,7 @@ static int builtin_diff_index(struct rev_info *revs,
 		perror("read_cache");
 		return -1;
 	}
-	return run_diff_index(revs, cached);
+	return run_diff_index(revs, option);
 }
 
 static int builtin_diff_tree(struct rev_info *revs,

diff-lib.c

@@ -512,9 +512,10 @@ static int diff_cache(struct rev_info *revs,
 	return unpack_trees(1, &t, &opts);
 }
 
-int run_diff_index(struct rev_info *revs, int cached)
+int run_diff_index(struct rev_info *revs, unsigned int option)
 {
 	struct object_array_entry *ent;
+	int cached = !!(option & DIFF_INDEX_CACHED);
 
 	if (revs->pending.nr != 1)
 		BUG("run_diff_index must be passed exactly one tree");

diff.h

@@ -585,7 +585,9 @@ const char *diff_aligned_abbrev(const struct object_id *sha1, int);
 /* report racily-clean paths as modified */
 #define DIFF_RACY_IS_MODIFIED 02
 int run_diff_files(struct rev_info *revs, unsigned int option);
-int run_diff_index(struct rev_info *revs, int cached);
+
+#define DIFF_INDEX_CACHED 01
+int run_diff_index(struct rev_info *revs, unsigned int option);
 
 int do_diff_cache(const struct object_id *, struct diff_options *);
 int diff_flush_patch_id(struct diff_options *, struct object_id *, int, int);