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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 2.41.0                        2023-06-01             GITPROTOCOL-COMMON(5)

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