First off I wanted to say this is amazing and I'm going to roll it into my current and future Makefiles. Second, if you're on OS X the `-P` flag is going to ha

First off I wanted to say this is amazing and I'm going to roll it into my current and future Makefiles. Second, if you're on OS X the `-P` flag is going to have problems [1]. Works fine if you just replace `grep -P` with something like `ack`! [1] http://stackoverflow.com/q/16658333/169153 http://stackoverflow.com/q/16658333/169153