Disable the pager when the output is not a tty

It would be advantageous for debugging purposes to avoid piping all output through a pager when the output isn't a tty, because less does its own buffering, so data doesn't always show up in the output right away.

For comparison, the git command checks whether it's output is a tty before spawning a pager: https://github.com/git/git/blob/f0294f474e16840f4efb3f4da3329ba46f53efa7/pager.c#L51