bug#27222: [PATCH] emacs-build-system install phase doesn't honor directory hierarchy

[Arun Isaac <arunisaac@systemreboot.net>]

> As far as I understand it, it was done for purpose: some packages
> include "uninteresting" (for tests, maintenance, etc.) *.el files in
> subdirs, that's why they are excluded by default.  So probably a better
> solution would be to fix 'ert-runner' package (as it is done in commit
> b1d32ec0e23bfec1dab4c56909228a494b2b0d60, for example).  WDYT?

I agree. The solution is to fix the ert-runner package, not the
emacs-build-system.

> This change also doesn't prevent excluding subfolders if they are truly
> unnecessary (such as tests subfolder), but this should happen due to
> explicit regexp in the exclude option, not because *all* subfolders are
> excluded.

We adopted the policy of excluding *all* subfolders from MELPA. From
their "Recipe Format" section at https://github.com/melpa/melpa

"Note that elisp in subdirectories is never included by default, so you
might find it convenient to separate auxiliiary files such as tests into
subdirectories to keep packaging simple."

I think this is a good policy. If we include subfolders by default,
we'll have to modify many packages with #:exclude arguments to get rid
of unnecessary subfolders. However, if we exclude subfolders by default,
we'll only have to modify fewer packages with #:include arguments.

> I also think these arguments are redundant!  I suggested to remove this
> duplication at:
>
>   https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26559#41

And, I did respond at
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26559#53

> ... but I think the include/exclude arguments need to be duplicated in
> two places. For example, look at arguments #:strip-flags and
> #:strip-directories in the `strip' phase of the gnu-build-system. Even
> there, the default values of the arguments are repeated in two places.

Do you know of some way in which we can avoid duplication of the
arguments? Even the gnu-build-system duplicates default values of
arguments.