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c5aecfc866
Currently we detect the hash algorithm in use by the length of the object ID. This is inelegant and prevents us from using a different hash algorithm that is also 256 bits in length. Since we cannot extend the v2 format in a backward-compatible way, let's add a v3 format, which is identical, except for the addition of capabilities, which are prefixed by an at sign. We add "object-format" as the only capability and reject unknown capabilities, since we do not have a network connection and therefore cannot negotiate with the other side. For compatibility, default to the v2 format for SHA-1 and require v3 for SHA-256. In t5510, always use format v3 so we can be sure we produce consistent results across hash algorithms. Since head -n N lists the top N lines instead of the Nth line, let's run our output through sed to normalize it and compare it against a fixed value, which will make sure we get exactly what we're expecting. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Reviewed-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
77 lines
2.6 KiB
Plaintext
77 lines
2.6 KiB
Plaintext
= Git bundle v2 format
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The Git bundle format is a format that represents both refs and Git objects.
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== Format
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We will use ABNF notation to define the Git bundle format. See
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protocol-common.txt for the details.
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A v2 bundle looks like this:
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----
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bundle = signature *prerequisite *reference LF pack
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signature = "# v2 git bundle" LF
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prerequisite = "-" obj-id SP comment LF
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comment = *CHAR
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reference = obj-id SP refname LF
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pack = ... ; packfile
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----
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A v3 bundle looks like this:
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----
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bundle = signature *capability *prerequisite *reference LF pack
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signature = "# v3 git bundle" LF
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capability = "@" key ["=" value] LF
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prerequisite = "-" obj-id SP comment LF
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comment = *CHAR
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reference = obj-id SP refname LF
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key = 1*(ALPHA / DIGIT / "-")
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value = *(%01-09 / %0b-FF)
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pack = ... ; packfile
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----
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== Semantics
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A Git bundle consists of several parts.
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* "Capabilities", which are only in the v3 format, indicate functionality that
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the bundle requires to be read properly.
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* "Prerequisites" lists the objects that are NOT included in the bundle and the
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reader of the bundle MUST already have, in order to use the data in the
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bundle. The objects stored in the bundle may refer to prerequisite objects and
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anything reachable from them (e.g. a tree object in the bundle can reference
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a blob that is reachable from a prerequisite) and/or expressed as a delta
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against prerequisite objects.
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* "References" record the tips of the history graph, iow, what the reader of the
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bundle CAN "git fetch" from it.
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* "Pack" is the pack data stream "git fetch" would send, if you fetch from a
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repository that has the references recorded in the "References" above into a
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repository that has references pointing at the objects listed in
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"Prerequisites" above.
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In the bundle format, there can be a comment following a prerequisite obj-id.
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This is a comment and it has no specific meaning. The writer of the bundle MAY
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put any string here. The reader of the bundle MUST ignore the comment.
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=== Note on the shallow clone and a Git bundle
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Note that the prerequisites does not represent a shallow-clone boundary. The
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semantics of the prerequisites and the shallow-clone boundaries are different,
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and the Git bundle v2 format cannot represent a shallow clone repository.
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== Capabilities
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Because there is no opportunity for negotiation, unknown capabilities cause 'git
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bundle' to abort. The only known capability is `object-format`, which specifies
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the hash algorithm in use, and can take the same values as the
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`extensions.objectFormat` configuration value.
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