Add support for `tmux` Control Mode

[zadjii-msft]

From discussion in #532, #1000:

If we're looking at tmux for things like splits, why not implement Tmux Control Mode like iTerm on MacOS. I switch back and forth between my Macs (with iTerm2) and my Surface Laptop with WSL but WSL2 combined with a really usable terminal (comparable to iTerm2) would really make me consider leaving the Apple camp.

In #532, from @zadjii-msft:

I did not know that Tmux Control Mode even existed. That sounds really awesome, I'm totally on board with trying to make that work somehow.

Was there any further thought put into this? I love tmux control mode - it's literally the only thing keeping me tethered to MacOS at work (since only iTerm supports it, and iTerm is mac-only). If it were implemented, I'd trash my Mac and request a Windows laptop immediately.

I'd love to see it listed as a post-1.0 milestone :)

We should do this.

Docs link: https://github.com/tmux/tmux/wiki/Control-Mode

[nicm]

Control mode isn't documented all that well but it isn't terribly complicated, if you want to do it you can feel free to ask me if you have questions.

[DHowett-MSFT]

@nicm Thanks! Maybe we can contribute a bit to the existence of control mode docs while we're at it. 😄

[nicm]

That would be great. There is an overview in the manual and it is easy enough to play with interactively using "tmux -C new" (instead of -CC). Plus iTerm2 has an implementation of the client side of course.

[ArcticLight]

I was actually just looking at Tmux Control Mode for work (which led me to this issue from Google) - this would be something I would really support! That, and there are already library implementations which might help; as @nicm mentioned iTerm2 implements control mode, and also I found this python library https://libtmux.git-pull.com/en/latest/ which implements the control mode client, too.

[nicm]

I don't think libtmux uses control mode.

[nicm]

I have written a wiki entry about control mode, although it doesn't have an awful lot more than is in the manual at the moment. Still suggestions welcome - https://github.com/tmux/tmux/wiki/Control_Mode.