postmodern/chgems — pull request #10 by jwilkins (2013-06-18 21:49:54+00:00)
Title: call bash as bash so [[ works

Bash features are unavailable when bash is invoked as /bin/sh
Alternative would be to make the script more sh compatible, but doubt that's necessary.
http://wiki.bash-hackers.org/scripting/bashbehaviour