Smarter close tab with confirmation

[tmillr]

Ideas

• with shell integration driven confirm and close, also ask for confirmation when at shell prompt && there are also background jobs still running or stopped (e.g. I could have an instance of vim suspended/stopped in the background and would unknowingly lose it by closing the tab)

• instead of just saying "n windows are running", be more specific and list all the programs that are running in that tab too (perhaps again including/considering background jobs as well)

[kovidgoyal]

Patches welcome. Here is a outline for how to implement it. 1) Write cross platform code to list all background processes that are descendants of a given PID. For example: https://unix.stackexchange.com/questions/701938/how-do-i-list-all-background-processes Except on Linux you would use the /proc file system directly and macOS you would use the process query library (cant recall what its called). See the implementation of process_group_map() to get started. No clue what you would do on the various BSDs. At least some of them support /proc. 2) Use this code to check if there background processes and also to list all processes associated with all windows. 3) Write a kitten to present the list of processes from (2) and ask for confirmation, since the current ask kitten cant really do that well. Or maybe add a mode to the ask kitten for it.