Use built-in query building function

[basil-conto]

The function url-build-query-string generalises ghub--url-encode-params, but expects a list of true lists, rather than cons pairs.

[basil-conto]

Alternatively:

(require 'map)

;;; ...

(defun ghub--url-encode-params (params)
  (url-build-query-string (map-apply #'list params)))

[tarsius]

If we could just replace ghub--url-encode-params with url-build-query-string, then I would be in favor of that. But we can't because the latter expects a format that doesn't match our public interface.

I might also be okay with replacing ghub--url-encode-params with (url-build-query-string (map-apply #'list params)), directly in ghub--request. But we can't because map isn't available in all Emacsen that we support.

Since we cannot actually remove ghub--url-encode-params, I want to keep the explicit and easy to understand implementation instead of redirecting to the much more complicated url-build-query-string.

[basil-conto]

Thanks, I appreciate and understand your reservations.

I just have one question - AFAICT, map.el was included in Emacs precisely between versions 24.5-rc2 and 25.1.91, and ghub.el depends on Emacs 25. Does this mean that there are versions of Emacs v such that 25 <= v < 25.1.91 which ghub.el officially supports but which lack map.el? Or am I missing / have I misunderstood something?

[basil-conto]

I just remembered that this PR also includes the change s/cl-delete/assq-delete-all/. I think this should be applied regardless of the URL parameter encoding, as cl-lib/cl-seq is not explicitly loaded. The alternative would be to load one of these, but I would argue that is unnecessary in the face of an equivalent built-in function. Should I break this change out into a separate PR? (I seem to have a problem with almost-atomic-PRs.)

[tarsius]

I've added the dependency on cl-lib. assq-delete-all is a bit to peculiar for my taste, it handles a very narrow use-case and it also is the only assq-* function.