create a command-line editor command (or option to "open") that is blocking until the tab is closed (and says so)

[williamstein]

The application of this would be to make it so you can use cocalc's graphical editor for the command line EDITOR env var, e.g., for git commits, etc.

I imagine something like

open --interactive filename

will:

1. Open the file as usual, but NOT terminate the open command
2. Show a special message at the top of the editor
3. Closing the tab will save the file and the open command will only then terminate

then you we could make the default for EDITOR be export EDITOR="open -i" or something like that...