Merge branch 'jk/harden-protocol-v2-delim-handling'

The server-end of the v2 protocol to serve "git clone" and "git fetch" was not prepared to see a delim packets at unexpected places, which led to a crash. * jk/harden-protocol-v2-delim-handling: test-lib-functions: simplify packetize() stdin code upload-pack: handle unexpected delim packets test-lib-functions: make packetize() more efficient