Merge branch 'rs/combine-diff-with-incompatible-options' into maint

Certain diff options are currently ignored when combined-diff is
shown; mark them as incompatible with the feature.
source: <220524.86v8tuvfl1.gmgdl@evledraar.gmail.com>

* rs/combine-diff-with-incompatible-options:
  combine-diff: abort if --output is given
  combine-diff: abort if --ignore-matching-lines is given

combine-diff.c

@@ -1498,6 +1498,13 @@ void diff_tree_combined(const struct object_id *oid,
 	int i, num_paths, needsep, show_log_first, num_parent = parents->nr;
 	int need_generic_pathscan;
 
+	if (opt->ignore_regex_nr)
+		die("combined diff and '%s' cannot be used together",
+		    "--ignore-matching-lines");
+	if (opt->close_file)
+		die("combined diff and '%s' cannot be used together",
+		    "--output");
+
 	/* nothing to do, if no parents */
 	if (!num_parent)
 		return;