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addad10594
Separating out the implementation of the handshake when starting a
long-running subprocess (for example, as is done for a clean/smudge
filter) was done in commit fa64a2fdbe ("sub-process: refactor
handshake to common function", 2017-07-26), but its documentation still
resides in gitattributes. Split out the documentation as well.
Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
50 lines
1.9 KiB
Text
50 lines
1.9 KiB
Text
Long-running process protocol
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=============================
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This protocol is used when Git needs to communicate with an external
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process throughout the entire life of a single Git command. All
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communication is in pkt-line format (see technical/protocol-common.txt)
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over standard input and standard output.
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Handshake
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---------
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Git starts by sending a welcome message (for example,
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"git-filter-client"), a list of supported protocol version numbers, and
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a flush packet. Git expects to read the welcome message with "server"
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instead of "client" (for example, "git-filter-server"), exactly one
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protocol version number from the previously sent list, and a flush
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packet. All further communication will be based on the selected version.
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The remaining protocol description below documents "version=2". Please
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note that "version=42" in the example below does not exist and is only
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there to illustrate how the protocol would look like with more than one
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version.
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After the version negotiation Git sends a list of all capabilities that
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it supports and a flush packet. Git expects to read a list of desired
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capabilities, which must be a subset of the supported capabilities list,
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and a flush packet as response:
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------------------------
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packet: git> git-filter-client
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packet: git> version=2
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packet: git> version=42
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packet: git> 0000
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packet: git< git-filter-server
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packet: git< version=2
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packet: git< 0000
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packet: git> capability=clean
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packet: git> capability=smudge
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packet: git> capability=not-yet-invented
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packet: git> 0000
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packet: git< capability=clean
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packet: git< capability=smudge
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packet: git< 0000
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------------------------
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Shutdown
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--------
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Git will close
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the command pipe on exit. The filter is expected to detect EOF
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and exit gracefully on its own. Git will wait until the filter
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process has stopped.
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