diff: make -O and --output work in subdirectory

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/am.c

@@ -1653,7 +1653,7 @@ static int fall_back_threeway(const struct am_state *state, const char *index_pa
 
 		init_revisions(&rev_info, NULL);
 		rev_info.diffopt.output_format = DIFF_FORMAT_NAME_STATUS;
-		diff_opt_parse(&rev_info.diffopt, &diff_filter_str, 1);
+		diff_opt_parse(&rev_info.diffopt, &diff_filter_str, 1, rev_info.prefix);
 		add_pending_sha1(&rev_info, "HEAD", our_tree, 0);
 		diff_setup_done(&rev_info.diffopt);
 		run_diff_index(&rev_info, 1);

diff-no-index.c

@@ -254,7 +254,8 @@ void diff_no_index(struct rev_info *revs,
 		else if (!strcmp(argv[i], "--"))
 			i++;
 		else {
-			j = diff_opt_parse(&revs->diffopt, argv + i, argc - i);
+			j = diff_opt_parse(&revs->diffopt, argv + i, argc - i,
+					   revs->prefix);
 			if (j <= 0)
 				die("invalid diff option/value: %s", argv[i]);
 			i += j;

diff.c

@@ -3695,12 +3695,16 @@ static int parse_ws_error_highlight(struct diff_options *opt, const char *arg)
 	return 1;
 }
 
-int diff_opt_parse(struct diff_options *options, const char **av, int ac)
+int diff_opt_parse(struct diff_options *options,
+		   const char **av, int ac, const char *prefix)
 {
 	const char *arg = av[0];
 	const char *optarg;
 	int argcount;
 
+	if (!prefix)
+		prefix = "";
+
 	/* Output format options */
 	if (!strcmp(arg, "-p") || !strcmp(arg, "-u") || !strcmp(arg, "--patch")
 	    || opt_arg(arg, 'U', "unified", &options->context))
@@ -3917,7 +3921,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "--pickaxe-regex"))
 		options->pickaxe_opts |= DIFF_PICKAXE_REGEX;
 	else if ((argcount = short_opt('O', av, &optarg))) {
-		options->orderfile = optarg;
+		const char *path = prefix_filename(prefix, strlen(prefix), optarg);
+		options->orderfile = xstrdup(path);
 		return argcount;
 	}
 	else if ((argcount = parse_long_opt("diff-filter", av, &optarg))) {
@@ -3956,9 +3961,10 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 	else if (!strcmp(arg, "--no-function-context"))
 		DIFF_OPT_CLR(options, FUNCCONTEXT);
 	else if ((argcount = parse_long_opt("output", av, &optarg))) {
-		options->file = fopen(optarg, "w");
+		const char *path = prefix_filename(prefix, strlen(prefix), optarg);
+		options->file = fopen(path, "w");
 		if (!options->file)
-			die_errno("Could not open '%s'", optarg);
+			die_errno("Could not open '%s'", path);
 		options->close_file = 1;
 		return argcount;
 	} else

diff.h

@@ -268,7 +268,7 @@ extern int parse_long_opt(const char *opt, const char **argv,
 extern int git_diff_basic_config(const char *var, const char *value, void *cb);
 extern int git_diff_ui_config(const char *var, const char *value, void *cb);
 extern void diff_setup(struct diff_options *);
-extern int diff_opt_parse(struct diff_options *, const char **, int);
+extern int diff_opt_parse(struct diff_options *, const char **, int, const char *);
 extern void diff_setup_done(struct diff_options *);
 
 #define DIFF_DETECT_RENAME	1

revision.c

@@ -2049,7 +2049,7 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
 	} else if (!strcmp(arg, "--ignore-missing")) {
 		revs->ignore_missing = 1;
 	} else {
-		int opts = diff_opt_parse(&revs->diffopt, argv, argc);
+		int opts = diff_opt_parse(&revs->diffopt, argv, argc, revs->prefix);
 		if (!opts)
 			unkv[(*unkc)++] = arg;
 		return opts;

t/t4056-diff-order.sh

@@ -68,6 +68,12 @@ test_expect_success POSIXPERM,SANITY 'unreadable orderfile' '
 	test_must_fail git diff -Ounreadable_file --name-only HEAD^..HEAD
 '
 
+test_expect_success "orderfile using option from subdir with --output" '
+	mkdir subdir &&
+	git -C subdir diff -O../order_file_1 --output ../actual --name-only HEAD^..HEAD &&
+	test_cmp expect_1 actual
+'
+
 for i in 1 2
 do
 	test_expect_success "orderfile using option ($i)" '