git-annex/doc/internals/git-remote-annex.mdwn
Joey Hess c7731cdbd9
add Backend.GitRemoteAnnex
Making GITBUNDLE be in the backend list allows those keys to be
hashed to verify, both when git-remote-annex downloads them, and by other
transfers and by git fsck.

GITMANIFEST is not in the backend list, because those keys will never be
stored in .git/annex/objects and can't be verified in any case.

This does mean that git-annex version will include GITBUNDLE in the list
of backends.

Also documented these in backends.mdwn

Sponsored-by: Kevin Mueller on Patreon
2024-05-07 13:54:08 -04:00

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Markdown

This adds two new key types to git-annex, GITMANIFEST and a GITBUNDLE.
GITMANIFEST--$UUID is the manifest for a git repository stored in the
git-annex repository with that UUID.
GITBUNDLE--$UUID-sha256 is a git bundle.
# format of the manifest file
An ordered list of bundle keys, one per line.
(Lines end with unix `"\n"`, not `"\r\n"`.)
# fetching
1. download GITMANIFEST for the uuid of the special remote
2. download each listed GITBUNDLE key that we don't have
3. `git fetch` from each new bundle in order
(note that later bundles can update refs from the versions in previous
bundles)
# pushing (incrementally)
This is how pushes are usually done.
1. create git bundle of all refs that are being pushed and have changed,
and objects since the previously pushed refs
2. hash to calculate GITBUNDLE key
3. upload GITBUNDLE key
4. download current manifest
5. append GITBUNDLE key to manifest
# pushing (full)
Note that this can be used to replace incrementals with a single bundle for
performance. It is also the only way to handle a push that deletes a
previously pushed ref.
1. create git bundle containing all refs stored in the repository, and all
objects
2. hash to calculate GITBUNDLE key name
3. upload GITBUNDLE key
4. download old manifest
4. upload new manifest listing only the single new GITBUNDLE
5. delete all other GITBUNDLEs that were listed in the old manifest
# multiple GITMANIFEST files
Usually there will only be one per special remote, but it's possible for
multiple special remotes to point to the same object storage, and if so
multiple GITMANIFEST objects can be stored.
It follows that the UUID of the special remote has to be included in the
annex:// uri, to know which GITMANIFEST to use when cloning from it.