Merge branch 'cc/replace-graft-peel-tags'

When given a tag that points at a commit-ish, "git replace --graft"
failed to peel the tag before writing a replace ref, which did not
make sense because the old graft mechanism the feature wants to
mimick only allowed to replace one commit object with another.
This has been fixed.

* cc/replace-graft-peel-tags:
  replace: peel tag when passing a tag first to --graft
  replace: peel tag when passing a tag as parent to --graft
  t6050: redirect expected error output to a file
  t6050: use test_line_count instead of wc -l

builtin/replace.c

@@ -370,16 +370,19 @@ static int replace_parents(struct strbuf *buf, int argc, const char **argv)
 	/* prepare new parents */
 	for (i = 0; i < argc; i++) {
 		struct object_id oid;
+		struct commit *commit;
+
 		if (get_oid(argv[i], &oid) < 0) {
 			strbuf_release(&new_parents);
 			return error(_("not a valid object name: '%s'"),
 				     argv[i]);
 		}
-		if (!lookup_commit_reference(the_repository, &oid)) {
+		commit = lookup_commit_reference(the_repository, &oid);
+		if (!commit) {
 			strbuf_release(&new_parents);
-			return error(_("could not parse %s"), argv[i]);
+			return error(_("could not parse %s as a commit"), argv[i]);
 		}
-		strbuf_addf(&new_parents, "parent %s\n", oid_to_hex(&oid));
+		strbuf_addf(&new_parents, "parent %s\n", oid_to_hex(&commit->object.oid));
 	}
 
 	/* replace existing parents with new ones */
@@ -478,15 +481,18 @@ static int create_graft(int argc, const char **argv, int force, int gentle)
 
 	strbuf_release(&buf);
 
-	if (oideq(&old_oid, &new_oid)) {
+	if (oideq(&commit->object.oid, &new_oid)) {
 		if (gentle) {
-			warning(_("graft for '%s' unnecessary"), oid_to_hex(&old_oid));
+			warning(_("graft for '%s' unnecessary"),
+				oid_to_hex(&commit->object.oid));
 			return 0;
 		}
-		return error(_("new commit is the same as the old one: '%s'"), oid_to_hex(&old_oid));
+		return error(_("new commit is the same as the old one: '%s'"),
+			     oid_to_hex(&commit->object.oid));
 	}
 
-	return replace_object_oid(old_ref, &old_oid, "replacement", &new_oid, force);
+	return replace_object_oid(old_ref, &commit->object.oid,
+				  "replacement", &new_oid, force);
 }
 
 static int convert_graft_file(int force)

t/t6050-replace.sh

@@ -40,7 +40,8 @@ commit_peeling_shows_parents ()
 	test "$_found" = "$_parent" || return 1
 	_parent_number=$(( $_parent_number + 1 ))
     done &&
-    test_must_fail git rev-parse --verify $_commit^$_parent_number
+    test_must_fail git rev-parse --verify $_commit^$_parent_number 2>err &&
+    test_i18ngrep "Needed a single revision" err
 }
 
 commit_has_parents ()
@@ -393,16 +394,40 @@ test_expect_success 'replace ref cleanup' '
 '
 
 test_expect_success '--graft with and without already replaced object' '
-	test $(git log --oneline | wc -l) = 7 &&
+	git log --oneline >log &&
+	test_line_count = 7 log &&
 	git replace --graft $HASH5 &&
-	test $(git log --oneline | wc -l) = 3 &&
+	git log --oneline >log &&
+	test_line_count = 3 log &&
 	commit_has_parents $HASH5 &&
 	test_must_fail git replace --graft $HASH5 $HASH4 $HASH3 &&
 	git replace --force -g $HASH5 $HASH4 $HASH3 &&
 	commit_has_parents $HASH5 $HASH4 $HASH3 &&
 	git replace -d $HASH5
 '
 
+test_expect_success '--graft using a tag as the new parent' '
+	git tag new_parent $HASH5 &&
+	git replace --graft $HASH7 new_parent &&
+	commit_has_parents $HASH7 $HASH5 &&
+	git replace -d $HASH7 &&
+	git tag -a -m "annotated new parent tag" annotated_new_parent $HASH5 &&
+	git replace --graft $HASH7 annotated_new_parent &&
+	commit_has_parents $HASH7 $HASH5 &&
+	git replace -d $HASH7
+'
+
+test_expect_success '--graft using a tag as the replaced object' '
+	git tag replaced_object $HASH7 &&
+	git replace --graft replaced_object $HASH5 &&
+	commit_has_parents $HASH7 $HASH5 &&
+	git replace -d $HASH7 &&
+	git tag -a -m "annotated replaced object tag" annotated_replaced_object $HASH7 &&
+	git replace --graft annotated_replaced_object $HASH5 &&
+	commit_has_parents $HASH7 $HASH5 &&
+	git replace -d $HASH7
+'
+
 test_expect_success GPG 'set up a signed commit' '
 	echo "line 17" >>hello &&
 	echo "line 18" >>hello &&