GITPROTOCOL-COMMON(5) Git Manual GITPROTOCOL-COMMON(5)
NAME
gitprotocol-common - Things common to various protocols
SYNOPSIS
<over-the-wire-protocol>
DESCRIPTION
This document sets defines things common to various over-the-wire
protocols and file formats used in Git.
ABNF NOTATION
ABNF notation as described by RFC 5234 is used within the protocol
documents, except the following replacement core rules are used:
HEXDIG = DIGIT / "a" / "b" / "c" / "d" / "e" / "f"
We also define the following common rules:
NUL = %x00
zero-id = 40*"0"
obj-id = 40*(HEXDIGIT)
refname = "HEAD"
refname /= "refs/" <see discussion below>
A refname is a hierarchical octet string beginning with "refs/" and not
violating the git-check-ref-format command’s validation rules. More
specifically, they:
1. They can include slash / for hierarchical (directory) grouping, but
no slash-separated component can begin with a dot ..
2. They must contain at least one /. This enforces the presence of a
category like heads/, tags/ etc. but the actual names are not
restricted.
3. They cannot have two consecutive dots .. anywhere.
4. They cannot have ASCII control characters (i.e. bytes whose values
are lower than \040, or \177 DEL), space, tilde ~, caret ^, colon
:, question-mark ?, asterisk *, or open bracket [ anywhere.
5. They cannot end with a slash / or a dot ..
6. They cannot end with the sequence .lock.
7. They cannot contain a sequence @{.
8. They cannot contain a \\.
PKT-LINE FORMAT
Much (but not all) of the payload is described around pkt-lines.
A pkt-line is a variable length binary string. The first four bytes of
the line, the pkt-len, indicates the total length of the line, in
hexadecimal. The pkt-len includes the 4 bytes used to contain the
length’s hexadecimal representation.
A pkt-line MAY contain binary data, so implementors MUST ensure
pkt-line parsing/formatting routines are 8-bit clean.
A non-binary line SHOULD BE terminated by an LF, which if present MUST
be included in the total length. Receivers MUST treat pkt-lines with
non-binary data the same whether or not they contain the trailing LF
(stripping the LF if present, and not complaining when it is missing).
The maximum length of a pkt-line’s data component is 65516 bytes.
Implementations MUST NOT send pkt-line whose length exceeds 65520
(65516 bytes of payload + 4 bytes of length data).
Implementations SHOULD NOT send an empty pkt-line ("0004").
A pkt-line with a length field of 0 ("0000"), called a flush-pkt, is a
special case and MUST be handled differently than an empty pkt-line
("0004").
pkt-line = data-pkt / flush-pkt
data-pkt = pkt-len pkt-payload
pkt-len = 4*(HEXDIG)
pkt-payload = (pkt-len - 4)*(OCTET)
flush-pkt = "0000"
Examples (as C-style strings):
pkt-line actual value
---------------------------------
"0006a\n" "a\n"
"0005a" "a"
"000bfoobar\n" "foobar\n"
"0004" ""
GIT
Part of the git(1) suite
Git 2.39.2 02/28/2023 GITPROTOCOL-COMMON(5)
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