Clean up some unnecessary Pathname usage
pygobject: fix patch SHA-1

Closes #28040.
mpd: add mirror.
first try at a ry formula
update to v0.4.1, and add a note about ry fullpath
use v0.4.2 and add a v
use HOMEBREW_PREFIX (i.e. /usr/local) for install
add a sha1
slim down the caveats
use double-quotes
use separate arguments for system calls
make ruby-build a recommended dependency
add a `head` link
use `prefix` instead of `HOMEBREW_PREFIX`
fully specify the binary path in the test
use a &> redirect instead of two separate redirects
use ry 0.5.0 for new installation dirs
use the fancy division operator to run ry ls
use ry v0.5.1
use v0.5.2