Remove execution of git

[justinrubek]

#2 implements a receive_pack route handler that simply passes the received data to a child process. I'd like to attempt to store the data without relying on git.

The method to do this is unclear currently but it seems gitoxide's git-pack may be of use https://docs.rs/git-pack/latest/git_pack/data/struct.Entry.html#method.from_bytes