Long-running process protocol ============================= This protocol is used when Git needs to communicate with an external process throughout the entire life of a single Git command. All communication is in pkt-line format (see linkgit:gitprotocol-common[5]) over standard input and standard output. Handshake --------- Git starts by sending a welcome message (for example, "git-filter-client"), a list of supported protocol version numbers, and a flush packet. Git expects to read the welcome message with "server" instead of "client" (for example, "git-filter-server"), exactly one protocol version number from the previously sent list, and a flush packet. All further communication will be based on the selected version. The remaining protocol description below documents "version=2". Please note that "version=42" in the example below does not exist and is only there to illustrate how the protocol would look like with more than one version. After the version negotiation Git sends a list of all capabilities that it supports and a flush packet. Git expects to read a list of desired capabilities, which must be a subset of the supported capabilities list, and a flush packet as response: ------------------------ packet: git> git-filter-client packet: git> version=2 packet: git> version=42 packet: git> 0000 packet: git< git-filter-server packet: git< version=2 packet: git< 0000 packet: git> capability=clean packet: git> capability=smudge packet: git> capability=not-yet-invented packet: git> 0000 packet: git< capability=clean packet: git< capability=smudge packet: git< 0000 ------------------------ Shutdown -------- Git will close the command pipe on exit. The filter is expected to detect EOF and exit gracefully on its own. Git will wait until the filter process has stopped.