Fork channel

Create a new channel as a copy of main.

Rename channel

Rename main to:

Delete channel

Delete main? This cannot be undone.

is_target_environment_version.c
// RUN: %clang_cc1 -fsyntax-only -triple x86_64-pc-windows-msvc18.0.0 -verify %s
// expected-no-diagnostics

#if !__is_target_environment(msvc)
  #error "mismatching environment"
#endif