vim.api.nvim_chan_send(vim.api.nvim_open_term(0), io.open("/path/to/smile.cat", "r"):read("*a"))

Problem:    Ex command info contains confusing information.
Solution:   When using the NOTADR flag use ADDR_OTHER for the address type.
            Cleanup code using NOTADR.  Check for errors in
            create_cmdidxs.vim.  Adjust Makefile to see the errors.
https://github.com/vim/vim/commit/b731689e85b4153af7edc8f0a6b9f99d36d8b011

Use Lua's "assert()" to make an invalid command definition
a compilation error.

Misc changes:

Remove 'RESTRICT' flag.
Neovim does not support "restricted" mode
since commit 7777532cebcfa9abc5ab2c7beae77f386feed3ca.

TODO:
Do not generate files before Lua assertions
so that CMake always runs the generator script
if the previous build has an invalid command definition.

Patch 8.1.1241 is too hard to port in 1 commit.
https://github.com/neovim/neovim/pull/13079 is too hard to review
and seems to be blocked.

Use 'int' type for some  addr variables to suppress 'switch/case' warnings.

* improve error message to make it actionable

Required for patch v8.1.1769.

defsfile:write() is executed multiple times to append strings.
Some of these can be combined into a format string, wrapped in [[]].
It is easier to read and insert strings via "%s".

defsfile now has a trailing comma for "cmdnames" array
but it does not break the build.