tl26 pretest start

The repository for the TL26 pretest is ready for testing on most platforms:
  https://tug.org/texlive/pretest.html
The only platform not updated is x86_64-darwinlegacy;
I hope it will be done soon.

It may take a day or so for the current build (running now) to make it
to the TL pretest mirrors, which are listed here:
  https://tug.org/texlive/mirmon/
(More pretest mirrors are welcome, BTW. See that mirmon page for info.)

A start at the list of user news is at the end of the pretest page.(*)
Corrections and additions welcome. Most importantly, please test the new
binaries when you can and report problems, particularly (for LaTeX
users) with pdflatex-dev and lualatex-dev if possible (about -dev, see
https://tex.stackexchange.com/questions/506646).

Normal package updates uploaded to CTAN will be installed in both the
pretest and the regular (tlnet) repository for a while.

The TL guide, man pages, etc., are not yet updated. I'll be working on
this over the coming day. --thanks, karl.

(*) P.S. One known discrepancy: the news mentions a new program xdvipsk,
contributed thanks to Sigitas Tolusis and VTeX. That binary does not
exist yet for most platforms, and its runtime support files are not yet
installed. Hopefully it will all be functional soon. Meanwhile, for
those who are interested, you can read about it here:
https://tug.org/TUGboat/tb38-2/tb119tolusis.pdf