Improve color behavior when piping output or redirecting to file

[ErikSwan]

Currently, if using options that colorize the output, distribution doesn't player super nicely when piping its output to another command, or redirecting it to a file, due to the the shell escape sequences used for colorizing the output.

For example, if your default options have color enabled, and you redirect the output to a file, opening that file in a text editor results in something like this (note all of the escape sequences):

342191L:25�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:24�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:23�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:22�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:21�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:20�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:19�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:18�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:17�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:16�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:15�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:14�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:13�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:12�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m
342191L:11�[0m|�[32m1 �[35m(3.85%) �[34m█████████████████████▏�[0m

I propose extending the --color option to have three options, always, never, and auto, similar to POSIX tools like grep and ls. The auto option detects whether the output is a terminal, and only enables color if so.

[analou-cone]

In Perl:

sub I_am_interactive {
  local *TTY; # local file handle
  open(TTY, "/dev/tty") or die "can't open /dev/tty: $!";
  my $tpgrp = tcgetpgrp(fileno(TTY));
  my $pgrp = getpgrp();
  close TTY;
  return ($tpgrp == $pgrp);
}

In Python:

import sys
def i_am_interactive():
  return sys.stdout.isatty()