hgeditor

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.

#!/bin/sh
#
# This is an example of using HGEDITOR to create of diff to review the
# changes while committing.

# If you want to pass your favourite editor some other parameters
# only for Mercurial, modify this:
case "${EDITOR}" in
    "")
        EDITOR="vi"
        ;;
    emacs)
        EDITOR="$EDITOR -nw"
        ;;
    gvim|vim)
        EDITOR="$EDITOR -f -o"
        ;;
esac


HGTMP=""
cleanup_exit() {
    rm -rf "$HGTMP"
}

# Remove temporary files even if we get interrupted
trap "cleanup_exit" 0 # normal exit
trap "exit 255" HUP INT QUIT ABRT TERM

HGTMP=$(mktemp -d ${TMPDIR-/tmp}/hgeditor.XXXXXX)
[ x$HGTMP != x -a -d $HGTMP ] || {
  echo "Could not create temporary directory! Exiting." 1>&2
  exit 1
}

(
    grep '^HG: changed' "$1" | cut -b 13- | while read changed; do
        "$HG" diff "$changed" >> "$HGTMP/diff"
    done
)

cat "$1" > "$HGTMP/msg"

MD5=$(which md5sum 2>/dev/null) || \
    MD5=$(which md5 2>/dev/null)
[ -x "${MD5}" ] && CHECKSUM=`${MD5} "$HGTMP/msg"`
if [ -s "$HGTMP/diff" ]; then
    $EDITOR "$HGTMP/msg" "$HGTMP/diff" || exit $?
else
    $EDITOR "$HGTMP/msg" || exit $?
fi
[ -x "${MD5}" ] && (echo "$CHECKSUM" | ${MD5} -c >/dev/null 2>&1 && exit 13)

mv "$HGTMP/msg" "$1"

exit $?