mxcl/homebrew — pull request #10753 by isao (2012-03-07 18:05:26+00:00)
Title: New Formula: wait_on - watch files or dirs from shell scripts without polling

From the man page: The wait_on command waits for something to happen to
the files or directories given as arguments and then exits. It is
anticipated that the wait_on command will be called from a shell script,
allowing, for example, a script to sleep until files have been added to
a directory or data is appended to a file.

** No polling is required **

(I had made a functionally identical pull request last night-- I just removed some params that were not needed, but botched the pull-request update..)