[Snek] mu, network REPL, echoing

[Misha Gusarov]

Hi Keith,

On 11 Oct 2020, at 3:40, Keith Packard wrote:

> It could? But the USB serial Snek instances all handle echo and erase
> stuff inside the device, so presumably the EV3 port should as well?
>
> You'll find the echo and erase code in 'snek-io.c', which gets hooked 
> up
> in stdio for the avrlibc and picolibc ports, and as SNEK_GETC for the
> esp32 port. Lots of options for how to connect things up here :-)

Oh, now it all makes sense.

So it follows ev3 port ought to have three modes:

- Non-interactive, reading script from stdin or a file
- Interactive, terminal. Leaves echoing and line editing to the 
terminal, handles prompt.
- Interactive, remote. Hadles echoing, line editing, prompt.

Sounds about right?

Non-interactive is selected by passing a filename. Should "remote" be 
selected
by testing for absence of controlling tty, os is it better to have an 
option
to enable it?

snekserver will then pass this option.

Best,
Misha.