The previous tests assumed default locations for all commands, however
they do not exist in the same place on all *nixes. I encountered this
when the test was failing on MacOSX where it was expected hardcoded
`/bin/sed` when in fact the code was identifying the correct local
expansion of `/usr/bin/sed`.
To make this test more robust, it now checks for the original location
of all cmds and uses that in its expansion tests for
`test_shell_command_wrapping()`.
Darwin actually symlinks /var inside /private, but mktemp reports back
the logical pathat time of file creation. So make sure we always get
the full physical path to be absolutely certain when doing comparisons
later, because thats how the Ruby status_shortcuts.rb script is going to
obtain them.
`grep -P` gives access to the PCRE matching engine, which is nice,
however, the version of grep shipped on many BSD systems (including
Darwin) does not have this flag.
Currently, `grep -P` was being used in the `_includes()` test helper.
For cross platform compatibility in tests, do not rely upon this option.
Luckily, all existing tests seem to work fine without it already!
