1Documentation Common to Pack and Http Protocols 2=============================================== 3 4ABNF Notation 5------------- 6 7ABNF notation as described by RFC 5234 is used within the protocol documents, 8except the following replacement core rules are used: 9---- 10 HEXDIG = DIGIT / "a" / "b" / "c" / "d" / "e" / "f" 11---- 12 13We also define the following common rules: 14---- 15 NUL = %x00 16 zero-id = 40*"0" 17 obj-id = 40*(HEXDIGIT) 18 19 refname = "HEAD" 20 refname /= "refs/" <see discussion below> 21---- 22 23A refname is a hierarchical octet string beginning with "refs/" and 24not violating the 'git-check-ref-format' command's validation rules. 25More specifically, they: 26 27. They can include slash `/` for hierarchical (directory) 28 grouping, but no slash-separated component can begin with a 29 dot `.`. 30 31. They must contain at least one `/`. This enforces the presence of a 32 category like `heads/`, `tags/` etc. but the actual names are not 33 restricted. 34 35. They cannot have two consecutive dots `..` anywhere. 36 37. They cannot have ASCII control characters (i.e. bytes whose 38 values are lower than \040, or \177 `DEL`), space, tilde `~`, 39 caret `^`, colon `:`, question-mark `?`, asterisk `*`, 40 or open bracket `[` anywhere. 41 42. They cannot end with a slash `/` or a dot `.`. 43 44. They cannot end with the sequence `.lock`. 45 46. They cannot contain a sequence `@{`. 47 48. They cannot contain a `\\`. 49 50 51pkt-line Format 52--------------- 53 54Much (but not all) of the payload is described around pkt-lines. 55 56A pkt-line is a variable length binary string. The first four bytes 57of the line, the pkt-len, indicates the total length of the line, 58in hexadecimal. The pkt-len includes the 4 bytes used to contain 59the length's hexadecimal representation. 60 61A pkt-line MAY contain binary data, so implementors MUST ensure 62pkt-line parsing/formatting routines are 8-bit clean. 63 64A non-binary line SHOULD BE terminated by an LF, which if present 65MUST be included in the total length. Receivers MUST treat pkt-lines 66with non-binary data the same whether or not they contain the trailing 67LF (stripping the LF if present, and not complaining when it is 68missing). 69 70The maximum length of a pkt-line's data component is 65520 bytes. 71Implementations MUST NOT send pkt-line whose length exceeds 65524 72(65520 bytes of payload + 4 bytes of length data). 73 74Implementations SHOULD NOT send an empty pkt-line ("0004"). 75 76A pkt-line with a length field of 0 ("0000"), called a flush-pkt, 77is a special case and MUST be handled differently than an empty 78pkt-line ("0004"). 79 80---- 81 pkt-line = data-pkt / flush-pkt 82 83 data-pkt = pkt-len pkt-payload 84 pkt-len = 4*(HEXDIG) 85 pkt-payload = (pkt-len - 4)*(OCTET) 86 87 flush-pkt = "0000" 88---- 89 90Examples (as C-style strings): 91 92---- 93 pkt-line actual value 94 --------------------------------- 95 "0006a\n" "a\n" 96 "0005a" "a" 97 "000bfoobar\n" "foobar\n" 98 "0004" "" 99----