1Long-running process protocol 2============================= 3 4This protocol is used when Git needs to communicate with an external 5process throughout the entire life of a single Git command. All 6communication is in pkt-line format (see technical/protocol-common.txt) 7over standard input and standard output. 8 9Handshake 10--------- 11 12Git starts by sending a welcome message (for example, 13"git-filter-client"), a list of supported protocol version numbers, and 14a flush packet. Git expects to read the welcome message with "server" 15instead of "client" (for example, "git-filter-server"), exactly one 16protocol version number from the previously sent list, and a flush 17packet. All further communication will be based on the selected version. 18The remaining protocol description below documents "version=2". Please 19note that "version=42" in the example below does not exist and is only 20there to illustrate how the protocol would look like with more than one 21version. 22 23After the version negotiation Git sends a list of all capabilities that 24it supports and a flush packet. Git expects to read a list of desired 25capabilities, which must be a subset of the supported capabilities list, 26and a flush packet as response: 27------------------------ 28packet: git> git-filter-client 29packet: git> version=2 30packet: git> version=42 31packet: git> 0000 32packet: git< git-filter-server 33packet: git< version=2 34packet: git< 0000 35packet: git> capability=clean 36packet: git> capability=smudge 37packet: git> capability=not-yet-invented 38packet: git> 0000 39packet: git< capability=clean 40packet: git< capability=smudge 41packet: git< 0000 42------------------------ 43 44Shutdown 45-------- 46 47Git will close 48the command pipe on exit. The filter is expected to detect EOF 49and exit gracefully on its own. Git will wait until the filter 50process has stopped.