You can use zlib-flate, like this:

    cat .git/objects/c0/fb67ab3fda7909000da003f4b2ce50a53f43e7 | zlib-flate -uncompress; echo

It's there by default on my machine, but it's part of `qpdf -  tools for and transforming and inspecting PDF files` if you need to install it.

I've popped an `echo` on the end of the command, as it's easier to read the output that way.