bug#81627: 30.2; [ELPA] Suggestions from my first ELPA package submission

> 1. Support comments in .elpaignore.

Currently, `.elpaignore` is passed straight to `tar` via its `-X`
option, so the best place to add support for comments would be in `tar`
(tho it would take years before we can start using that feature).  🙁

> 2. Document what should and should not be added to .elpaignore, maybe
>    with reasoning.

What *should* be there are files that would be actively harmful.
These fall typically into two categories:
- Files which aren't needed but would, say, double the size of the
  tarball (typical example: snapshots or the copy of the GPL for <20kB
  packages).  20% size increase is negligible, OTOH, so that doesn't
  count as "should".
- Files which would cause technical problems once installed, e.g. test
  or maintenance files that may fail to compile on the end-user machine
  because they require packages that aren't in the `Package-Requires:`.

Beyond that, it's up to the package maintainer (I recommend not adding
anything beyond that, simply to minimize the maintenance burden of
that `.elpaignore` file).

> - Should .dir-locals.el be excluded?

Can't see any benefit, no.

> - Probably .elpaignore itself should be excluded.

Can't see any benefit, no.

> - Probably README.org should be excluded since the tarball already has
>   the rendered/exported README-elpa.

Unless the README is unusually large compared to the rest, I ... can't
see any benefit, no.

>   Also document relevant export
>   options. Give guidance for how to organize the content of README.org.

I have very little knowledge about that, so wouldn't know what to say,
but feel free to suggest things.


=== Stefan