peel_onion(): add support for <rev>^{tag}

rhansen · gitster · commit 75aa26d34c4a · 2013-09-03T13:09:17.000-07:00
Complete the <rev>^{<type>} family of object descriptors by having <rev>^{tag} dereference <rev> until a tag object is found (or fail if unable). At first glance this may not seem very useful, as commits, trees, and blobs cannot be peeled to a tag, and a tag would just peel to itself. However, this can be used to ensure that <rev> names a tag object: $ git rev-parse --verify v1.8.4^{tag} 04f013d $ git rev-parse --verify master^{tag} error: master^{tag}: expected tag type, but the object dereferences to tree type fatal: Needed a single revision Users can already ensure that <rev> is a tag object by checking the output of 'git cat-file -t <rev>', but: * users may expect <rev>^{tag} to exist given that <rev>^{commit}, <rev>^{tree}, and <rev>^{blob} all exist * this syntax is more convenient/natural in some circumstances Signed-off-by: Richard Hansen <rhansen@bbn.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
@@ -121,6 +121,9 @@ some output processing may assume ref names in UTF-8.
 object that exists, without requiring 'rev' to be a tag, and
 without dereferencing 'rev'; because a tag is already an object,
 it does not have to be dereferenced even once to get to an object.
++
+'rev{caret}\{tag\}' can be used to ensure that 'rev' identifies an
+existing tag object.
 
 '<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
   A suffix '{caret}' followed by an empty brace pair
diff --git a/sha1_name.c b/sha1_name.c
@@ -679,6 +679,8 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
 	sp++; /* beginning of type name, or closing brace for empty */
 	if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 		expected_type = OBJ_COMMIT;
+	else if (!strncmp(tag_type, sp, 3) && sp[3] == '}')
+		expected_type = OBJ_TAG;
 	else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 		expected_type = OBJ_TREE;
 	else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
diff --git a/t/t1511-rev-parse-caret.sh b/t/t1511-rev-parse-caret.sh
@@ -54,6 +54,13 @@ test_expect_success 'ref^{tree}' '
 	test_must_fail git rev-parse blob-tag^{tree}
 '
 
+test_expect_success 'ref^{tag}' '
+	test_must_fail git rev-parse HEAD^{tag} &&
+	git rev-parse commit-tag >expected &&
+	git rev-parse commit-tag^{tag} >actual &&
+	test_cmp expected actual
+'
+
 test_expect_success 'ref^{/.}' '
 	git rev-parse master >expected &&
 	git rev-parse master^{/.} >actual &&
