apply: --build-fake-ancestor expects blobs

The "index" line read from the patch to reconstruct a partial
preimage tree records the object names of blob objects.

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

builtin/apply.c

@@ -3203,7 +3203,7 @@ static void build_fake_ancestor(struct patch *list, const char *filename)
 		name = patch->old_name ? patch->old_name : patch->new_name;
 		if (0 < patch->is_new)
 			continue;
-		else if (get_sha1(patch->old_sha1_prefix, sha1))
+		else if (get_sha1_blob(patch->old_sha1_prefix, sha1))
 			/* git diff has no index line for mode/type changes */
 			if (!patch->lines_added && !patch->lines_deleted) {
 				if (get_current_sha1(patch->old_name, sha1))

t/t1512-rev-parse-disambiguation.sh

@@ -54,7 +54,7 @@ test_expect_success 'disambiguate tree-ish' '
 	git rev-parse --verify 000000000:a0blgqsjc
 '
 
-test_expect_failure 'disambiguate blob' '
+test_expect_success 'disambiguate blob' '
 	sed -e "s/|$//" >patch <<-EOF &&
 	diff --git a/frotz b/frotz
 	index 000000000..ffffff 100644