#!/bin/bash

findmaster() {
# search the master branch by reading .gitmodules
cat "$2/.gitmodules" | \
while read line
do
	a=($line)
	if [ "${a[0]}" == "[submodule" ]; then
		[ "$seen" == "1" ] && return
		[ "[submodule \"$1\"]" == "$line" ] && seen=1
	else
		[ "${a[0]}" == "branch" ] && [ "$seen" == "1" ] && { echo ${a[2]}; return; }
	fi
done
}

parselog() {
# collect the commit messages
git log | \
while read line
do
	a=($line)
	if [ "${a[0]}" == "commit" ]; then
		x=${a[1]}
		[ "$x" == "$1" ] && { echo -e $msg | sort -u ; break; }
		while read line
		do
			[ "$line" == "" ] && break
		done
	else
		msg="$msg\n$line"
	fi
done
}

export script=$(readlink -f $0)

if [ "$2" == "" ]; then
	# make the latest commit in each submodule of branch mainbranch the current revision in each submodule
	mainbranch=$(git branch | grep \* | cut -d ' ' -f2) 
	# reset submodules to last revision
	git pull
	git submodule update
	# call me for each submodule
	git submodule foreach "$script \"\$name\" \"\$toplevel\" \"$mainbranch\" \"$1\""
	# submodules are at most recent positions
	if [ "$1" != "" ]; then
		# now the merged submodules are added. stash these changes, merge the branch, pop stash and commit
		git stash
		git merge "$1"
		git stash pop
		git commit -m "@S updated submodule references"
		git push
	fi
	git commit -m "@S updated submodule references"
	git push
else
	# called from git submodule above
	# make the latest commit in this branch $3 the current revision in this submodule
	# get current revision
	revision=$(git rev-parse HEAD)
	
	if [ "$3" == "master" ]; then
		branch=$(findmaster "$1" "$2")
		[ "$branch" == "" ] && branch=master
	else
		branch="$3"		
	fi
	
	# switch to branch and check it out, then pull if branch exists
	git checkout $branch || exit 0
	git pull
	
	head=$(git rev-parse HEAD)
	
	if [ "$revision" != "$head" ]; then
		echo scanning from $revision to $head
		# get the log messages in between
		msg=$(parselog $revision)
		if [ "$msg" != "" ]; then
			# commit the changes to the master module
			pushd "$2"
			git add "$1"
			git commit -m "@S $1:$msg"
			popd
		fi
	fi
	
	# branch is now up to date
	if [ "$4" != "" ]; then
		# merge specified branch into "master / what's defined in .gitmodules"
		git merge "$4" || exit 0
		git push
		# add the changes to the master module
		pushd "$2"
		git add "$1"
		popd		
	fi
fi