Fork channel

Create a new channel as a copy of main.

Rename channel

Rename main to:

Delete channel

Delete main? This cannot be undone.

strip-underscore-default-darwin.test
REQUIRES: system-darwin

## Show that on darwin, the default is to strip the leading underscore.

RUN: llvm-cxxfilt __Z1fv _Z2bav | FileCheck %s
CHECK: f()
CHECK: _Z2bav