Documentation/technical/bundle-format.txt

   1 = Git bundle v2 format
   2
   3 The Git bundle format is a format that represents both refs and Git objects.
   4
   5 == Format
   6
   7 We will use ABNF notation to define the Git bundle format. See
   8 protocol-common.txt for the details.
   9
  10 A v2 bundle looks like this:
  11
  12 ----
  13 bundle    = signature *prerequisite *reference LF pack
  14 signature = "# v2 git bundle" LF
  15
  16 prerequisite = "-" obj-id SP comment LF
  17 comment      = *CHAR
  18 reference    = obj-id SP refname LF
  19
  20 pack         = ... ; packfile
  21 ----
  22
  23 A v3 bundle looks like this:
  24
  25 ----
  26 bundle    = signature *capability *prerequisite *reference LF pack
  27 signature = "# v3 git bundle" LF
  28
  29 capability   = "@" key ["=" value] LF
  30 prerequisite = "-" obj-id SP comment LF
  31 comment      = *CHAR
  32 reference    = obj-id SP refname LF
  33 key          = 1*(ALPHA / DIGIT / "-")
  34 value        = *(%01-09 / %0b-FF)
  35
  36 pack         = ... ; packfile
  37 ----
  38
  39 == Semantics
  40
  41 A Git bundle consists of several parts.
  42
  43 * "Capabilities", which are only in the v3 format, indicate functionality that
  44         the bundle requires to be read properly.
  45
  46 * "Prerequisites" lists the objects that are NOT included in the bundle and the
  47   reader of the bundle MUST already have, in order to use the data in the
  48   bundle. The objects stored in the bundle may refer to prerequisite objects and
  49   anything reachable from them (e.g. a tree object in the bundle can reference
  50   a blob that is reachable from a prerequisite) and/or expressed as a delta
  51   against prerequisite objects.
  52
  53 * "References" record the tips of the history graph, iow, what the reader of the
  54   bundle CAN "git fetch" from it.
  55
  56 * "Pack" is the pack data stream "git fetch" would send, if you fetch from a
  57   repository that has the references recorded in the "References" above into a
  58   repository that has references pointing at the objects listed in
  59   "Prerequisites" above.
  60
  61 In the bundle format, there can be a comment following a prerequisite obj-id.
  62 This is a comment and it has no specific meaning. The writer of the bundle MAY
  63 put any string here. The reader of the bundle MUST ignore the comment.
  64
  65 === Note on the shallow clone and a Git bundle
  66
  67 Note that the prerequisites does not represent a shallow-clone boundary. The
  68 semantics of the prerequisites and the shallow-clone boundaries are different,
  69 and the Git bundle v2 format cannot represent a shallow clone repository.
  70
  71 == Capabilities
  72
  73 Because there is no opportunity for negotiation, unknown capabilities cause 'git
  74 bundle' to abort.  The only known capability is `object-format`, which specifies
  75 the hash algorithm in use, and can take the same values as the
  76 `extensions.objectFormat` configuration value.