fix(prompting): ensure ps_esc doesn't escape backslashes
fix(prompting): ensure ps_esc doesn't escape backslashes

Add a `sed_vuf` alias that will do a "visually unambigous format" `sed`
invocation that does behave accordant with the specs.

On Mac OS X it turns out that `sed l` doesn't escape backslashes; undoubtedly, this is a bug.

cueedee/.ix