I set it up so that TIOCSWINSZ on a master PTY gets forwarded to the slave.
This feels intuitively right. Terminal can then use that to inform the shell
or whoever is inside the slave that the window size has changed.
TIOCSWINSZ also triggers the generation of a SIGWINCH signal. :^)
(Don't) use this to implement short-form output in ls.
I'm too tired to make a nice column formatting algorithm.
I just wanted something concise when I type "ls".
