summaryrefslogtreecommitdiff
path: root/Documentation/technical/protocol-common.txt
blob: bf30167ae3590c97100beaea7070645a6da124a3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
Documentation Common to Pack and Http Protocols
===============================================
 
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:
 
. They can include slash `/` for hierarchical (directory)
  grouping, but no slash-separated component can begin with a
  dot `.`.
 
. They must contain at least one `/`. This enforces the presence of a
  category like `heads/`, `tags/` etc. but the actual names are not
  restricted.
 
. They cannot have two consecutive dots `..` anywhere.
 
. 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.
 
. They cannot end with a slash `/` or a dot `.`.
 
. They cannot end with the sequence `.lock`.
 
. They cannot contain a sequence `@{`.
 
. 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 65520 bytes.
Implementations MUST NOT send pkt-line whose length exceeds 65524
(65520 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"            ""
----