hgeditor

showstack: also handle SIGALRM

This is looking *very* handy when debugging mysterious hangs in a
test: you can wrap a hanging invocation in

  `perl -e 'alarm shift @ARGV; exec @ARGV' 1`

for example, a hanging `hg pull` becomes

  `perl -e 'alarm shift @ARGV; exec @ARGV' 1 hg pull`

where the `1` is the timeout in seconds before the process will be hit
with SIGALRM. After making that edit to the test file, you can then
use --extra-config-opt on run-tests.py to globaly enable showstack
during the test run, so you'll get full stack traces as you force your
hg to exit.

I wonder (but only a little, not enough to take action just yet) if we
should wire up some scaffolding in run-tests itself to automatically
wrap all commands in alarm(3) somehow to avoid hangs in the future?

Differential Revision: https://phab.mercurial-scm.org/D4870

#!/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 $?