Merge branch 'ps/ban-a-or-o-operator-with-test'

Merge branch 'ps/ban-a-or-o-operator-with-test'

Test and shell scripts clean-up.

* ps/ban-a-or-o-operator-with-test:
  Makefile: stop using `test -o` when unlinking duplicate executables
  contrib/subtree: convert subtree type check to use case statement
  contrib/subtree: stop using `-o` to test for number of args
  global: convert trivial usages of `test <expr> -a/-o <expr>`