Help a sed noob

Hi,

There is a construct like this in git-parse-remote.sh which makes busybox ash unhappy:

                sed -ne '/^URL: */{
                        s///p
                        q
                }' "$GIT_DIR/remotes/$1"

It complains about "no previous regexp" while gnu sed is ok. Can anyone explain to me what does "s///p" do? GNU Sed info page says nothing about empty regexp. If I replace it with "s/\(.*\)/\1/p" then I get "URL: " along with the remote path.

By the way, can we use another construct instead? It would be less work for me ;-)