#!/bin/bash

#
# Goes through the ensure-follows branches and makes sure
# the non-excused branches have it merged.
#

die() {
	echo >&2 "$@"
	exit 1
}

attempt_merge() {
	source_branch=$1
	remote_branch=$2

	if [ "$source_branch" == "$remote_branch" ] ; then
		return
	fi
	if [[ $excused =~ " $remote_branch " ]] ; then
		return
	fi
	git branch -r --contains "$source_branch" | grep --quiet "origin/$remote_branch"
	if [ $? -eq 0 ] ; then
		return
	fi

	echo -n "Merging $source_branch into $remote_branch..."

	baserev=$(git merge-base "$source_branch" "origin/$remote_branch")
	git read-tree -m --trivial $baserev "origin/$remote_branch" "$source_branch"
	if [ $? -ne 0 ] ; then
		echo "failed merge"
		return
	fi

	new_tree=$(git write-tree)
	new_commit=$(git commit-tree $new_tree -p "origin/$remote_branch" -p "$source_branch" <<FOO
Merge $source_branch into $remote_branch
FOO)
	if [ "$new_commit" == "" ] ; then
		echo "failed commit"
		return
	fi

	git push origin "$new_commit:$remote_branch" >/dev/null 2>/dev/null
	if [ $? -ne 0 ] ; then
		echo "failed push"
		return
	fi

	echo "succeeded"
}

gitconfig=$(git rev-parse origin/gitconfig)
if [ $? -ne 0 ] ; then
	echo "gitconfig branch not found"
	exit 1
fi

# The source branches
config_hash=$(git ls-tree $gitconfig | grep config | grep -oP '\w{40}')
branches=$(git cat-file blob "$config_hash" | grep hooks.update-ensure-follows.branches)
branches=("${branches#*=}")
excused=$(git cat-file blob "$config_hash" | grep hooks.update-ensure-follows.excused)
excused=" ${excused#*=} "

# We're going to merge stuff into the index, so make sure it's okay
git diff-index --cached --quiet HEAD -- || die "refusing to refollow--your index is not clean"

# Get the latest remote refs
git fetch

# So we can put the index back after we screw with it
original_head=$(git rev-parse HEAD)

for source_branch in ${branches[@]} ; do
	git branch -r | grep -v HEAD | while read line ; do
		if [[ "$line" =~ origin/(.*) ]] ; then
			attempt_merge $source_branch ${BASH_REMATCH[1]}
		fi
	done
done

# Put the index back
git read-tree "$original_head"