fast-import: add tests for tagging blobs

fast-import allows to create an annotated tag that annotates a blob,
via mark or direct sha1 specification.

For mark it works, for sha1 it tries to read the object. It tries to
do so via read_sha1_file, and then checks the size to be at least 46.

That's weird, let's just allow to (annotated) tag any object referenced
by sha1. If the object originates from our packfile, we still fail though.

Signed-off-by: Dmitry Ivankov <divanorama@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

fast-import.c

@@ -2688,13 +2688,9 @@ static void parse_new_tag(void)
 		type = oe->type;
 		hashcpy(sha1, oe->idx.sha1);
 	} else if (!get_sha1(from, sha1)) {
-		unsigned long size;
-		char *buf;
-
-		buf = read_sha1_file(sha1, &type, &size);
-		if (!buf || size < 46)
-			die("Not a valid commit: %s", from);
-		free(buf);
+		type = sha1_object_info(sha1, NULL);
+		if (type < 0)
+			die("Not a valid object: %s", from);
 	} else
 		die("Invalid ref name or SHA1 expression: %s", from);
 	read_next_command();

t/t9300-fast-import.sh

@@ -94,6 +94,12 @@ data <<EOF
 An annotated tag without a tagger
 EOF
 
+tag series-A-blob
+from :3
+data <<EOF
+An annotated tag that annotates a blob.
+EOF
+
 INPUT_END
 test_expect_success \
     'A: create pack from stdin' \
@@ -151,6 +157,18 @@ test_expect_success 'A: verify tag/series-A' '
 	test_cmp expect actual
 '
 
+cat >expect <<EOF
+object $(git rev-parse refs/heads/master:file3)
+type blob
+tag series-A-blob
+
+An annotated tag that annotates a blob.
+EOF
+test_expect_success 'A: verify tag/series-A-blob' '
+	git cat-file tag tags/series-A-blob >actual &&
+	test_cmp expect actual
+'
+
 cat >expect <<EOF
 :2 `git rev-parse --verify master:file2`
 :3 `git rev-parse --verify master:file3`
@@ -169,6 +187,29 @@ test_expect_success \
 		</dev/null &&
 	test_cmp expect marks.new'
 
+test_tick
+cat >input <<INPUT_END
+tag series-A-blob-2
+from $(git rev-parse refs/heads/master:file3)
+data <<EOF
+Tag blob by sha1.
+EOF
+INPUT_END
+
+cat >expect <<EOF
+object $(git rev-parse refs/heads/master:file3)
+type blob
+tag series-A-blob-2
+
+Tag blob by sha1.
+EOF
+
+test_expect_success \
+	'A: tag blob by sha1' \
+	'git fast-import <input &&
+	git cat-file tag tags/series-A-blob-2 >actual &&
+	test_cmp expect actual'
+
 test_tick
 cat >input <<INPUT_END
 commit refs/heads/verify--import-marks