#!/bin/sh

#
# Some docs
#
# A --- B --- C    stable
# |\         /
# | D ----- E      topic1
#  \       /
#   F --- G        topic2
#
# topic1 stable result
#  D      A      contains, merge base=A
#  D      C      contains, merge base=A
#  E      A      contains, merge base=E
#  E      C      contains, merge base=A

#
# * --- * --------- *   stable
# |\     \
# | A --- B ---- C      topic1
# \             /
#  D --- E --- F        topic2
#
# F: contains=topic1,topic2
# C: contains=topic1

head=$(git rev-parse HEAD)

# Watch out for the very first commit in the repo because we use head^
# Hopefully we can optimize this away later.
git rev-parse --verify --quiet "$head^" >/dev/null
if [ $? -ne 0 ] ; then
	echo "0"
	exit 0
fi

contains=($(git branch -r --contains $head))
if [ ${#contains[@]} -eq 0 ] ; then
	echo "$head has not been pushed"
	exit 1
fi

potential=" "
for branch in ${contains[@]} ; do
	branch=${branch##origin/}
	#echo "branch=$branch"

	# Walk back until we hit a baserev that is not the branch_tip itself (because it was merged)
	branch_tip=$(git rev-parse origin/$branch)
	stable_rev=$(git rev-parse origin/stable)
	stable_base=$(git merge-base "$branch_tip" "$stable_rev")

	# echo "stable_base=$stable_base"
	while [ "$stable_base" == "$branch_tip" ] ; do
		stable_rev=$(git rev-parse "${stable_rev}^")
		stable_base=$(git merge-base "$branch_tip" "$stable_rev")
	done
	# echo "stable_base=$stable_base"

	git rev-list --first-parent $stable_base..$branch_tip | grep --quiet "$head"
	if [ $? -eq 0 ] ; then
		if [ "$branch" == "stable" ] ; then
			describe=$(git describe $head 2>/dev/null)
			if [ $? -eq 0 ] ; then
				potential="$potential $describe"
			else
				potential="$potential stable-$head"
			fi
		else
			number=$(git rev-list --first-parent "$stable_base..$head" | wc -l)
			potential="$potential $branch-$number"
		fi
	fi
done

potential=($potential)
if [ ${#potential[@]} -eq 1 ] ; then
	echo "${potential[0]}"
else
	echo "unknown"
fi