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