| 1 | Long-running process protocol |
| 2 | ============================= |
| 3 | |
| 4 | This protocol is used when Git needs to communicate with an external |
| 5 | process throughout the entire life of a single Git command. All |
| 6 | communication is in pkt-line format (see linkgit:gitprotocol-common[5]) |
| 7 | over standard input and standard output. |
| 8 | |
| 9 | Handshake |
| 10 | --------- |
| 11 | |
| 12 | Git starts by sending a welcome message (for example, |
| 13 | "git-filter-client"), a list of supported protocol version numbers, and |
| 14 | a flush packet. Git expects to read the welcome message with "server" |
| 15 | instead of "client" (for example, "git-filter-server"), exactly one |
| 16 | protocol version number from the previously sent list, and a flush |
| 17 | packet. All further communication will be based on the selected version. |
| 18 | The remaining protocol description below documents "version=2". Please |
| 19 | note that "version=42" in the example below does not exist and is only |
| 20 | there to illustrate how the protocol would look like with more than one |
| 21 | version. |
| 22 | |
| 23 | After the version negotiation Git sends a list of all capabilities that |
| 24 | it supports and a flush packet. Git expects to read a list of desired |
| 25 | capabilities, which must be a subset of the supported capabilities list, |
| 26 | and a flush packet as response: |
| 27 | |
| 28 | ------------------------ |
| 29 | packet: git> git-filter-client |
| 30 | packet: git> version=2 |
| 31 | packet: git> version=42 |
| 32 | packet: git> 0000 |
| 33 | packet: git< git-filter-server |
| 34 | packet: git< version=2 |
| 35 | packet: git< 0000 |
| 36 | packet: git> capability=clean |
| 37 | packet: git> capability=smudge |
| 38 | packet: git> capability=not-yet-invented |
| 39 | packet: git> 0000 |
| 40 | packet: git< capability=clean |
| 41 | packet: git< capability=smudge |
| 42 | packet: git< 0000 |
| 43 | ------------------------ |
| 44 | |
| 45 | Shutdown |
| 46 | -------- |
| 47 | |
| 48 | Git will close |
| 49 | the command pipe on exit. The filter is expected to detect EOF |
| 50 | and exit gracefully on its own. Git will wait until the filter |
| 51 | process has stopped. |