Merge branch 'jk/rev-parse-double-dashes' into maint

"git rev-parse <revs> -- <paths>" did not implement the usual
disambiguation rules the commands in the "git log" family used in
the same way.

* jk/rev-parse-double-dashes:
  rev-parse: be more careful with munging arguments
  rev-parse: correctly diagnose revision errors before "--"

builtin/rev-parse.c

@@ -279,6 +279,7 @@ static int try_difference(const char *arg)
 				exclude = n;
 			}
 		}
+		*dotdot = '.';
 		return 1;
 	}
 	*dotdot = '.';
@@ -302,8 +303,10 @@ static int try_parent_shorthands(const char *arg)
 		return 0;
 
 	*dotdot = 0;
-	if (get_sha1_committish(arg, sha1))
+	if (get_sha1_committish(arg, sha1)) {
+		*dotdot = '^';
 		return 0;
+	}
 
 	if (!parents_only)
 		show_rev(NORMAL, sha1, arg);
@@ -312,6 +315,7 @@ static int try_parent_shorthands(const char *arg)
 		show_rev(parents_only ? NORMAL : REVERSED,
 				parents->item->object.sha1, arg);
 
+	*dotdot = '^';
 	return 1;
 }
 
@@ -476,6 +480,7 @@ N_("git rev-parse --parseopt [options] -- [<args>...]\n"
 int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 {
 	int i, as_is = 0, verify = 0, quiet = 0, revs_count = 0, type = 0;
+	int has_dashdash = 0;
 	int output_prefix = 0;
 	unsigned char sha1[20];
 	const char *name = NULL;
@@ -489,6 +494,13 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 	if (argc > 1 && !strcmp("-h", argv[1]))
 		usage(builtin_rev_parse_usage);
 
+	for (i = 1; i < argc; i++) {
+		if (!strcmp(argv[i], "--")) {
+			has_dashdash = 1;
+			break;
+		}
+	}
+
 	prefix = setup_git_directory();
 	git_config(git_default_config, NULL);
 	for (i = 1; i < argc; i++) {
@@ -765,6 +777,8 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 		}
 		if (verify)
 			die_no_single_rev(quiet);
+		if (has_dashdash)
+			die("bad revision '%s'", arg);
 		as_is = 1;
 		if (!show_file(arg, output_prefix))
 			continue;

t/t1506-rev-parse-diagnosis.sh

@@ -196,4 +196,28 @@ test_expect_success 'dotdot is not an empty set' '
 	test_cmp expect actual
 '
 
+test_expect_success 'arg before dashdash must be a revision (missing)' '
+	test_must_fail git rev-parse foobar -- 2>stderr &&
+	test_i18ngrep "bad revision" stderr
+'
+
+test_expect_success 'arg before dashdash must be a revision (file)' '
+	>foobar &&
+	test_must_fail git rev-parse foobar -- 2>stderr &&
+	test_i18ngrep "bad revision" stderr
+'
+
+test_expect_success 'arg before dashdash must be a revision (ambiguous)' '
+	>foobar &&
+	git update-ref refs/heads/foobar HEAD &&
+	{
+		# we do not want to use rev-parse here, because
+		# we are testing it
+		cat .git/refs/heads/foobar &&
+		printf "%s\n" --
+	} >expect &&
+	git rev-parse foobar -- >actual &&
+	test_cmp expect actual
+'
+
 test_done