If it really is just a pinhole leak, I'm always surprised how well a
stainless steel hose clamp works with a little piece of rubber gasket
If you want to fix it permanently, break a hole in the concrete about
eight inches away, and then carefully work towards the pipe. Very gently,
chisel so that the pipe is clear from the concrete. There are various
types of transition fittings made for lead pipe that will go to copper or
threads. Usually, though, you'll have to bring in a little of the pipe so
it can be matched up.
Come to think of it, before you tackle this, make sure you can find a
place that sells these fittings (sometimes called "lead packs). They're
getting increasingly difficult to find.