In https://github.com/neovim/neovim/pull/22214, init_default_autocmds
has been turned into a lua function call to nvim_create_augroup and
nvim_create_autocmd.
This introduced a strange regression: a test in vim_spec.lua started
failing with its last_set_chan value switching from 0 to
-9223372036854775808.
It turns out that -9223372036854775808 is the value of LUA_INTERNAL_CALL
and would be inherited as last_set_chan by options set from the command
line due to the WITH_SCRIPT_CONTEXT macro not restoring the channel id
(WITH_SCRIPT_CONTEXT is used by nvim_create_augroup).
5ca6cf55f9