#!/bin/sh

# Command line
refname="$1"
oldrev="$2"
newrev="$3"

if expr "$oldrev" : '0*$' >/dev/null ; then
	exit 0
fi

git rev-parse --not --branches | git rev-list --stdin $oldrev..$newrev | while read commit ; do
	number_of_parents=$(git rev-list -n 1 --parents $commit | sed 's/ /\n/g' | grep -v $commit | wc -l)
	if [[ $number_of_parents > 1 ]] ; then
		# Find the original branch point (B)
		parents=$(git rev-list -n 1 --parents $commit | sed 's/ /\n/g' | grep -v $commit)
		baserev=$(git merge-base $parents)

		# For each parent
		git rev-list -n 1 --parents $commit | sed 's/ /\n/g' | grep -v $commit | while read parent ; do
			all_commits=$(git rev-list $baserev..$parent | wc -l)
			new_commits=$(git rev-parse --not --branches | git rev-list --stdin $baserev..$parent | wc -l)
			if [[ $all_commits -eq $new_commits ]] ; then
				echo "----------------------------------------------------"
				echo
				echo "It looks like you should rebase instead of merging $commit"
				echo
				echo "----------------------------------------------------"
				exit 1
			fi
		done
		if [ $? -ne 0 ] ; then
			exit 1
		fi
	fi
done