That allows tests to be completely independent of each other, so tests that
change global state — such as modify environment variables, define functions or
aliases, or hash commands — will not affect other tests, without needing an
explicit cleanup step.
This enables testing path-tilde-home with and without $HOME set, which is part
of issue #216.
While at it, convert the test harness to TAP. This fixes issue #180 by adding
support for "not ok 42 # TODO" output.
This commit assumes that 'grep' supports POSIX-compliant -q and -v flags.
Patch-by: Matthew Martin <phy1729@gmail.com>
Matthew Martin