Suggestion: A more flexible approach would make pre/post directories, 

do [[
                # maybe skip either the executable or README test?
                # or perhaps only match *.sh filenames instead
                # to reflect the in-shell sourcing?
                -x $hookfile &&
                $hookfile == ${hookfile#README} &&
                $hookfile == ${hookfile#.} &&
                $hookfile == ${hookfile%.bak} &&
                $hookfile == ${hookfile%\~}
        ]] && source "$hookfile"
done