branches can have '/'. So, just remove the 'refs/heads' prefix.
@ -16,7 +16,7 @@ gitsym=`git symbolic-ref HEAD`
case "$gitsym" in fatal*) exit 0 ;; esac
# the current branch is the tail end of the symbolic reference
branch="${gitsym##*/}" # get the basename after "refs/head/"
branch="${gitsym##refs/heads/}" # get the basename after "refs/heads/"
tmp="/tmp/$$-gitstatus.out"
trap "rm -f \"$tmp\"" EXIT