To be used to help simplify ports which install programmable shell completions. While the scope of this is relatively small, feedback is appreciated (and whether it's something that actually belongs).
Further context:
I've had a few hiccups with shell completions in particular [1][2], and thought it would be an idea to make it less error-prone and canonicalize the shell completion paths (in line with [3]), additionally creating the preliminary directories (if wanted).
[1] https://cgit.freebsd.org/ports/commit/?id=36d76902abf2cb2e16da2dd31cf38e58adaf37a7
[2] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=255384
[3] https://docs.freebsd.org/en/books/porters-handbook/special/#shell-completion