testing luahbtex based lualatex-dev

[David Carlisle]

Having just released LaTeX2e 2019-10-01 (and a couple of patch releases)
the LaTeX team are looking to re-issue the latex-dev formats with a
view to testing pre-release code aimed for a 2020 release and texlive
2020.

In the case of lualatex, we are planning to use luahbtex as the
underlying engine in 2020.
As of the latest luaotfload release, harf mode support is already
available by default in the main release on engines that support it.

luahbtex is available in tlcontrib but getting it from there and
running a luahblatex-dev version from that is sufficiently unusual
that in practice the luahbtex based format will get little testing
other than by the core developers until the full texlive 2020 release,
at which point it will already be the main lualatex.

Would it be possible (at least on the platforms where it is already in
tlcontrib) for the luahbtex binary to be included in texlive 2019 now,
along with configuring lualatex-dev to use it?

We know binaries are not normally added mid way during the year but
this would allow more testing of what is likely to be a major new
feature, so we thought it worth asking....

David
for the LaTeX project Team