You would need to build a new git with an updated openssl. I actually did build this (it builds updated openssl, openssh, curl and git binaries and statically links them so that they are drop-in replacements), and we'll see if it works. If it does, then I'll make it available. It has no dependencies other than Xcode 2.5.
Alternatively, you could update using MacPorts, though I imagine not much is checked against Tiger these days. I didn't have a good result trying to do this with Tigerbrew, which is why I did it myself.