git-sync-branches

function gitsync(){

	CURRENT=$(git branch --show-current)

	if [ -n "$1" ]
	then
		echo "Fetching branch $1"
		git fetch origin $1:$1
		echo "Merging $1 into $CURRENT"
		git merge $1 -m "Merged branch $1 into $CURRENT"
		echo "Pushing changes"
		git push
		git checkout $CURRENT
	else
		echo "Missing branch name to sync from"
	fi
}

alias sync=gitsync

You can use rebase at line 10 if wanted to as well, depends on your strategy