LUA boot loader coming very soon

Greetings,

As you may know, the Lua (http://www.lua.org) boot loader has been in the
works for some time. It started out life as a GSoC in 2014 by Pedro Souza
mentored by Wojciech A. Koszek. Rui Paulo created a svn project branch to
try to integrate it. I rebased that effort into a github branch which Pedro
Arthur fixed up. Over the past year, I've been cleaning up the boot loader
for other reasons, and found the time was ripe to start integrating this
into the tree. However, those integration efforts have taken a while as my
day-job work on the boot loader took priority. In the mean time, Ed Maste
and the FreeBSD Foundation funded Zakary Nafziger to enhance the original
GSoC Lua scripts to bring it closer to parity with the evolution of the
FORTH menu system since the GSoC project started.

I'm pleased to announce that all these threads of development have
converged and I'll be pushing the FreeBSD Lua Loader later today. This
loader uses Lua as its scripting language instead of FORTH. While
co-existance is planned, the timeline for it is looking to be a few weeks
and I didn't want to delay pushing this into the tree for that.

To try the loader, you'll need to build WITHOUT_FORTH=yes and
WITH_LOADER_LUA=yes. Fortunately, you needn't do a full world to do this,
you can do it in src/stand and install the result (be sure to have the
options for both the build and the install). This will replace your current
/boot/loader that is scripted with FORTH to one that's scripted with Lua.
It will install the lua scripts in /boot/lua. The boot is scripted with
/boot/lua/loader.lua instead of /boot/loader.rc. You are strongly advised
to create a backup copy of /boot/loader before testing (eg cp /boot/loader
/boot/loader_forth), since you'll need to boot that from boot2 if something
goes wrong. I've tested it extensively, though, with userboot.so and it's
test program, so all the initial kinks of finding the lua scripts, etc have
been worked out.

While it's possible to build all the /boot/loader variants with Lua, I've
just tested a BIOS booting /boot/loader both with and without menus
enabled. I've not tested any of the other variants and the instructions for
testing some of them may be rather tedious (especially UEFI, if you want a
simple path to back out). Since there's not been full convergence testing,
you'll almost certainly find bumps in this system. Also, all the
build-system APIs are likely not yet final.

I put  MFC after a month on the commit. Due to the heroic (dare I say
almost crazy) work of Kyle Evans on merging all the revs from -current to
11, I'm planning a MFC to 11 after the co-existence issues are hammered
out. In 11, FORTH will be the default, and Lua will  be built by default,
but users will have to do something to use it. 12, both FORTH and Lua will
be built and installed, with Lua as default (barring unforeseen
complications). Once the co-existence stuff goes in, I imagine we'll make
the switch to Lua by default shortly after that. In 13, FORTH will be
removed unless there's a really really compelling case made to keep it.

So please give it a spin and give me any feedback, documentation updates
and/or bug fixes. I'm especially interested in reviews from people that
have embedded Lua in other projects or experts in Lua that can improve the
robustness of the menu code.

Warner