Fork channel

Create a new channel as a copy of main.

Rename channel

Rename main to:

Delete channel

Delete main? This cannot be undone.

fat-threading.test
# By default, dsymutil spawns one thread per architecture and this test just
# ensures that things don't break when processing multiple archs.
# RUN: dsymutil -no-output %p/../Inputs/fat-test.arm.dylib -o /dev/null 2>&1