Create a new channel as a copy of main.
Rename main to:
Delete main? This cannot be undone.
// RUN: %clang -I%S/Before -index-header-map -I%S/Index -I%S/After %s -### 2>> %t.log // RUN: FileCheck %s < %t.log // CHECK: {{-I.*Before.*-index-header-map.*-I.*Index.*-I.*After}}