Create a new channel as a copy of main.
Rename main to:
Delete main? This cannot be undone.
// RUN: rm -rf %t // RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t -fmodule-name=TBranchProxy -emit-module -x c++ %S/Inputs/PR20786/module.modulemap