Fork channel

Create a new channel as a copy of main.

Rename channel

Rename main to:

Delete channel

Delete main? This cannot be undone.

symbolized-subtractor.test
# RUN: llvm-mc < %s --triple x86_64-apple-darwin -filetype=obj | llvm-objdump --macho -d - | FileCheck %s

nop
x:
leaq	x-y(%rax), %rbx
.data
y:
.quad 0

# CHECK: leaq	x-y(%rax), %rbx