Lua event handler for :terminal OSC codes, etc.

[justinmk]

see https://github.com/neovim/neovim/pull/4412#issuecomment-192544136

May help with https://github.com/neovim/neovim/issues/4349

problem

Lua/Vimscript plugins can't handle OSC codes emitted by :terminal programs.

solution

• set up Lua callback dispatch via vterm_state_set_unrecognised_fallbacks() ?
• also allow Lua handling of "known" terminal sequences / commands?
  • only for :terminal. Not needed for TUI because we have vim.ui_attach().

related

• https://github.com/neovim/neovim/pull/17197
• https://github.com/neovim/neovim/pull/16740
• https://github.com/neovim/neovim/pull/22159

[glacambre]

• set up Lua callback dispatch via vterm_state_set_unrecognised_fallbacks() ?
• also allow Lua handling of "known" terminal sequences / commands?

What do you think about creating autocommand events for these? I think it'd make sense now that autocommands are easy to interact with from Lua.

[justinmk]

OSC/DCS are now forwarded to the TermRequest autocmd event.