add --chmod: don't update index when --dry-run is used

`git add --chmod` applies the mode changes even when `--dry-run` is
used. Fix that and add some tests for this option combination.

Helped-by: Junio C Hamano <[email protected]>
Signed-off-by: Matheus Tavares <[email protected]>
Reviewed-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: matheustavares

builtin/add.c

@@ -38,17 +38,23 @@ struct update_callback_data {
 	int add_errors;
 };
 
-static void chmod_pathspec(struct pathspec *pathspec, char flip)
+static void chmod_pathspec(struct pathspec *pathspec, char flip, int show_only)
 {
 	int i;
 
 	for (i = 0; i < active_nr; i++) {
 		struct cache_entry *ce = active_cache[i];
+		int err;
 
 		if (pathspec && !ce_path_match(&the_index, ce, pathspec, NULL))
 			continue;
 
-		if (chmod_cache_entry(ce, flip) < 0)
+		if (!show_only)
+			err = chmod_cache_entry(ce, flip);
+		else
+			err = S_ISREG(ce->ce_mode) ? 0 : -1;
+
+		if (err < 0)
 			fprintf(stderr, "cannot chmod %cx '%s'\n", flip, ce->name);
 	}
 }
@@ -609,7 +615,7 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 		exit_status |= add_files(&dir, flags);
 
 	if (chmod_arg && pathspec.nr)
-		chmod_pathspec(&pathspec, chmod_arg[0]);
+		chmod_pathspec(&pathspec, chmod_arg[0], show_only);
 	unplug_bulk_checkin();
 
 finish:

t/t3700-add.sh

@@ -386,6 +386,26 @@ test_expect_success POSIXPERM 'git add --chmod=[+-]x does not change the working
 	! test -x foo4
 '
 
+test_expect_success 'git add --chmod honors --dry-run' '
+	git reset --hard &&
+	echo foo >foo4 &&
+	git add foo4 &&
+	git add --chmod=+x --dry-run foo4 &&
+	test_mode_in_index 100644 foo4
+'
+
+test_expect_success 'git add --chmod --dry-run reports error for non regular files' '
+	git reset --hard &&
+	test_ln_s_add foo foo4 &&
+	git add --chmod=+x --dry-run foo4 2>stderr &&
+	grep "cannot chmod +x .foo4." stderr
+'
+
+test_expect_success 'git add --chmod --dry-run reports error for unmatched pathspec' '
+	test_must_fail git add --chmod=+x --dry-run nonexistent 2>stderr &&
+	test_i18ngrep "pathspec .nonexistent. did not match any files" stderr
+'
+
 test_expect_success 'no file status change if no pathspec is given' '
 	>foo5 &&
 	>foo6 &&