chgserver: create new process group after fork (issue5051)...
chgserver: create new process group after fork (issue5051)
This is to make SIGTSTP work. Before the patch, the server process group is
considered "orphaned" and will ignore SIGTSTP, SIGTTIN, SIGTTOU, according to
POSIX. See the comment above `will_become_orphaned_pgrp` in `kernel/exit.c`
from Linux 4.3 for details.
SIGTSTP is important if chgserver runs some ncurses commend like `commit -i`.
Ncurses has its own SIGTSTP handler which will do the following:
1. Clean the screen
2. Stop itself by resending SIGTSTP to itself
3. Restore the screen
If SIGTSTP is ignored, step 2 will be a noop, which means the process cannot
be suspended properly.
In order to make things work, chg client needs to forward SIGTSTP and SIGCONT
to server as well.
