fixup! builtin rebase: call git am directly

In the scripted version, we call `move_to_original_branch`, which
updates `HEAD` to point to the original branch again, after updating
that branch to point at the current commit. This does not require any
worktree update.

In the built-in version, we tried to reuse the `reset_head()` function,
which however does try to update the worktree. Of course, as there are
no changes, no actual worktree updates are performed. However, with an
insanely large repository, even just looking whether we need to write
anything takes a noticeable time. So let's avoid that in the built-in
version, too.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

builtin/rebase.c

@@ -505,7 +505,8 @@ static int move_to_original_branch(struct rebase_options *opts)
 		    opts->head_name, oid_to_hex(&opts->onto->object.oid));
 	strbuf_addf(&head_reflog, "rebase finished: returning to %s",
 		    opts->head_name);
-	ret = reset_head(NULL, "checkout", opts->head_name, 0,
+	ret = reset_head(NULL, "checkout", opts->head_name,
+			 RESET_HEAD_REFS_ONLY,
 			 orig_head_reflog.buf, head_reflog.buf);
 
 	strbuf_release(&orig_head_reflog);