update.sh

#!/bin/bash
#
# Reject non-fastforward updates per branch
# Place it at hooks/update and make it executable

ref=$1
old=$2
new=$3

# Debug
#echo $@

# Only valid for master branch
[ $ref != "refs/heads/master" ] && exit 0

# First commit, skip fast
[ $old = "0000000000000000000000000000000000000000" ] && exit 0

# Delete operation, skip fast
[ $new = "0000000000000000000000000000000000000000" ] && echo "Delete master? Noop!" && exit 1

# Commits that are in old and not in new (non-fastforward)
missing=$(git rev-list "$old" ^"$new" |wc -l)

# Everything is ok, proceed
[ $missing -eq 0 ] && exit 0

echo
echo "[skroutz:git] Can't proceed with the push, non-fastforwared updates for $ref are prohibited ($missing commits would be lost)"
echo
echo
exit 1