bug#81332: info/dir and INFO_NONMISC are not gated by DOCLANGS

Hello,

The bug is closed and this is not a regression from the patches, so this is just a question: is the remaining DOCLANGS inconsistency worth fixing? I mentioned it when Vincent and I discussed the empty DOCLANGS case, and I said I could take it as a follow-up.

Two places still hardcode the three built-in manuals:

- srcdir_doc_info_dir_inputs lists doc/emacs/emacs.texi, doc/lispintro/emacs-lisp-intro.texi and doc/lispref/elisp.texi unconditionally, while the misc entries are gated (texi_misc_default only exists when default is in DOCLANGS)
- INFO_NONMISC lists the same three .info files for install-info

The visible effect is with DOCLANGS='fr' (or any set without default): emacs-info, lispintro-info and lispref-info are no-ops, so those manuals are never built, but info/dir still lists them, and install-info still runs install-info on them. The latter is invisible today only because the recipe ignores errors.

Gating both on $(filter default,$(DOCLANGS)) is a small change. One detail: build-aux/make-info-dir starts with "test $# -ge 2 || exit 1", so with empty DOCLANGS everything would be gated away and "make info" would fail instead of generating a dir file. I would relax that to -ge 1, so info/dir is still generated with the header and no entries.

If you think this is worth doing, I will send a patch. And if a closed bug is the wrong place for it, tell me and I will file a new report.

Cheers,
[email protected]