The formula for mg currently does not work for non /usr/local prefixes.
This patch fixes two issues:
- the Makefile checks for PREFIX, not prefix; and
- the bin dir must exist, otherwise install renames mg to bin.
Signed-off-by: Adam Vandenberg <flangy@gmail.com>
brewkit.rb changes ENV destructively, so lets not do that everytime a formula
is required. Now it's possible for other tools to require a formula
description without worrying about side-effects.
