sha1_loose_object_info(): do not return success on missing object

Since 052fe5ea (sha1_loose_object_info: make type lookup optional,
2013-07-12), sha1_loose_object_info() returns happily without
checking if the object in question exists, which is not what the the
caller sha1_object_info_extended() expects; the caller does not even
bother checking the existence of the object itself.

Noticed-by: Sven Brauch <svenbrauch@googlemail.com>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

sha1_file.c

@@ -2413,15 +2413,18 @@ static int sha1_loose_object_info(const unsigned char *sha1,
 
 	/*
 	 * If we don't care about type or size, then we don't
-	 * need to look inside the object at all.
+	 * need to look inside the object at all. Note that we
+	 * do not optimize out the stat call, even if the
+	 * caller doesn't care about the disk-size, since our
+	 * return value implicitly indicates whether the
+	 * object even exists.
 	 */
 	if (!oi->typep && !oi->sizep) {
-		if (oi->disk_sizep) {
-			struct stat st;
-			if (stat_sha1_file(sha1, &st) < 0)
-				return -1;
+		struct stat st;
+		if (stat_sha1_file(sha1, &st) < 0)
+			return -1;
+		if (oi->disk_sizep)
 			*oi->disk_sizep = st.st_size;
-		}
 		return 0;
 	}
 

t/t1006-cat-file.sh

@@ -179,6 +179,12 @@ test_expect_success "--batch-check for an emtpy line" '
     test " missing" = "$(echo | git cat-file --batch-check)"
 '
 
+test_expect_success 'empty --batch-check notices missing object' '
+	echo "$_z40 missing" >expect &&
+	echo "$_z40" | git cat-file --batch-check="" >actual &&
+	test_cmp expect actual
+'
+
 batch_input="$hello_sha1
 $commit_sha1
 $tag_sha1