Support for keyboard input

[georgecrawford]

This is a nice-to-have rather than an integral requirement for the tool, but I would be delighted if watchexec would incorporate the keyboard command listeners from tools like entr:

entr listens for keyboard input and responds to the following commands:

     SPACE       Execute the utility immediately.  If the `-r' option is set
                 this will terminate and restart the child process as if a
                 file change event had occurred.

     q           Quit; equivalent pressing Ctrl-C.

or nodemon:

Whilst nodemon is running, if you need to manually restart your application, 
instead of stopping and restart nodemon, you can simply type rs with a 
carriage return, and nodemon will restart your process.

This would take the developer experience to the next level!

Thanks again for a fantastic tool - I evaluated about 10 different file watch utilities, and this has the best combination of API, performance and functionality I've found.

[mattgreen]

Thanks for the kind words.

I like this idea, but currently the way it handles async is pretty ad-hoc at the moment. I'd like to move to Futures so I can easily wait on several sources of input easily, but that might not be until 2.0.

[passcod]

Thinking about this today: there should also be a key to pause running the command on changes. Unsure yet if it should be unpaused on the same key only or unpaused also by whatever key does a manual run.