Fork channel

Create a new channel as a copy of main.

Rename channel

Rename main to:

Delete channel

Delete main? This cannot be undone.

options-from-env.test
# RUN: env LLVM_SYMBOLIZER_OPTS='0 1 --verbose' llvm-symbolizer 2 | FileCheck %s
# RUN: env LLVM_ADDR2LINE_OPTS='0 1 --verbose' llvm-addr2line 2 | FileCheck %s

# CHECK:      0
# CHECK-NEXT: 1
# CHECK-NEXT: 2