git-sync

#!/bin/sh
set -e
#set -x

USB="$PWD"
WORK=$HOME/work
SYNC_TS=.git/sync.timestamp

[ -f .components ] && COMPONENTS="$(cat .components)"

if [ ! -z "$@" ];then
	COMPONENTS="$@"
fi

if [ -z "$COMPONENTS" ];then
	echo "No components specified."
	echo "List them in .components file or command line."
	exit 1
fi

checklocal(){
	local COMP=$1
	(
		test -d "$COMP" || return 0
		cd "$COMP"
		git diff --quiet || { echo 1; return 1; }
		git diff --quiet --cached || { echo 2; return 1; }
	)
}

compare(){
	local COMP=$1
	local MODIFIED=0
	test -d "$COMP" -o -f "$USB/$COMP.tar" || { echo 5; return 5; }
	test -d "$COMP" || { echo 1; return 1; }
	test -f "$USB/$COMP.tar" || { echo 2; return 2; }
	test -f "$COMP/$SYNC_TS"|| { echo 4; return 4; }
	local WORK_TS=$(find $COMP/.git/refs $COMP/.git/HEAD $COMP/.git/logs/refs/ -type f -printf '%T@ %p\n' | sort -rn | awk '{print $2;exit}')

	if [ "$USB/$COMP.tar" -nt "$COMP/$SYNC_TS" ]; then
		MODIFIED=$((MODIFIED + 1))
	fi
	if [ "$WORK_TS" -nt "$COMP/$SYNC_TS" ];then
		MODIFIED=$((MODIFIED + 2))
	fi

	echo $MODIFIED
	return $MODIFIED	
}

towork(){
	local COMP=$1
	test -f "$USB/$COMP.tar" || { echo "Fatal: $COMP not found on USB."; return 1; }
	rm -rf "$COMP/.git"
	tar xpf "$USB/$COMP.tar"
	{
		cd $COMP
		git reset --hard
		cd ..
	}
	touch -r "$USB/$COMP.tar" "$COMP/$SYNC_TS"
	return 0
}

tousb(){
	local COMP=$1
	rm -f "$USB/$COMP.tar" "$USB/$COMP.tar.tmp"
	tar cp "$COMP/.git" -f "$USB/$COMP.tar.tmp"
	touch -r "$USB/$COMP.tar.tmp" "$COMP/$SYNC_TS"
	mv "$USB/$COMP.tar.tmp" "$USB/$COMP.tar"
	return 0
}

process(){
	local COMP=$1
	
	local CHANGED=$(checklocal $COMP)
	case $CHANGED in
		1)	{ echo "$COMP: unstaged changes found, skipping."; return 1; }
			;;
		2)	{ echo "$COMP: uncommited changes found, skipping."; return 1; }
			;;
	esac

	local COMPARE=$(compare $COMP)
	case $COMPARE in
		0)	echo "$COMP is equal, skipping."
			;;
		1)	echo "$COMP is newer on USB, processing..."
			towork $COMP
			;;
		2)	echo "$COMP is newer in working dir, processing..."
			tousb $COMP
			;;
		3)	echo "$COMP was modified in both location, skipping."
			;;
		4)	echo "$COMP exists, but sync status is unknown, skipping."
			;;
		5)	echo "$COMP not exists in working dir nor on USB, skipping."
			;;
		*)	echo "unexpected"
			;;
	esac
}


cd "$WORK"

for COMP in $COMPONENTS;do
	COMP=${COMP%.tar}
	process $COMP||true
done

exit 0