rev-parse: A and B in "rev-parse A..B" refer to committish

Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin/rev-parse.c

@@ -238,7 +238,7 @@ static int try_difference(const char *arg)
 		next = "HEAD";
 	if (dotdot == arg)
 		this = "HEAD";
-	if (!get_sha1(this, sha1) && !get_sha1(next, end)) {
+	if (!get_sha1_committish(this, sha1) && !get_sha1_committish(next, end)) {
 		show_rev(NORMAL, end, next);
 		show_rev(symmetric ? NORMAL : REVERSED, sha1, this);
 		if (symmetric) {
@@ -278,7 +278,7 @@ static int try_parent_shorthands(const char *arg)
 		return 0;
 
 	*dotdot = 0;
-	if (get_sha1(arg, sha1))
+	if (get_sha1_committish(arg, sha1))
 		return 0;
 
 	if (!parents_only)

t/t1512-rev-parse-disambiguation.sh

@@ -111,7 +111,7 @@ test_expect_success 'log name1..name2 takes only commit-ishes on both ends' '
 	git log 000000000...
 '
 
-test_expect_failure 'rev-parse name1..name2 takes only commit-ishes on both ends' '
+test_expect_success 'rev-parse name1..name2 takes only commit-ishes on both ends' '
 	git rev-parse 000000000..000000000 &&
 	git rev-parse ..000000000 &&
 	git rev-parse 000000000..