Fix neglect of diff_setup()/diff_setup_done() symmetry.

Code that calls diff_setup(), including via init_revisions(), should later call
diff_setup_done(), possibly via setup_revisions(). Failure to do so could cause
errors, especially in the future when we add responsibilities to
diff_setup_done(). This instance causes no known errors with the present code.
But it resulted in an error with an experimental patch.

Signed-off-by: Keith Cascio <keith@cs.ucla.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-checkout.c

@@ -295,6 +295,8 @@ static void show_local_changes(struct object *head)
 	init_revisions(&rev, NULL);
 	rev.abbrev = 0;
 	rev.diffopt.output_format |= DIFF_FORMAT_NAME_STATUS;
+	if (diff_setup_done(&rev.diffopt) < 0)
+		die("diff_setup_done failed");
 	add_pending_object(&rev, head, NULL);
 	run_diff_index(&rev, 0);
 }