pathhack [-f] [+HACK|-HACK] [--] [COMMAND [ARGS...]]

Path hacks are stored in ~/bin/hacks.  `+HACK' adds a hack to the path,
`-HACK' removes it.  If a COMMAND is given, run the command with the
hacked path; otherwise set it in the current shell.

If `-f' is given, force reordering of added hacks; otherwise, if a hack
is already inserted, ignore it.

With no arguments, print the installed hacks in order.