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Romain Calascibetta 2022-10-24 11:06:44 +02:00
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# Git-kv, a simple Key-Value store synchronized with a Git repository
This library is a simple implementation of a Git repository that can be read
and/or modified. It offers two ways to create such a local repository:
1) The local repository can be created in a serialized state
2) The local repository can be created from a remote repository
The first method has the advantage of not requiring an internet connection. The
serialized state can be created with the `mgit` tool:
```sh
$ mgit https://github.com/mirage/mirage <<EOF
> save db.pack
> quit
$ ls db.pack
db.pack
```
The disadvantage is that the serialized state may be out of sync with the state
of the remote repository. In this case, the user has access to the `pull`
function, which allows the internet state of the local repository to be
re-synchronised with the remote repository.
```ocaml
let contents_of_file filename =
let ic = open_in filename in
let ln = in_channel_length ic in
let rs = Bytes.create ln in
really_input ic rs 0 ln ;
Bytes.unsafe_to_string rs
let _ =
Git_kv.of_octets ctx
~remote:"git@github.com:mirage/mirage.git"
(contents_of_file "db.pack") >>= fun t ->
Git_kv.pull t >>= fun diff ->
...
```
The second method initiates a connection to the remote repository in order to
download its state and reproduce a synchronised internal state. The type of
connections supported are described in the given `ctx`. We recommend the
tutorial about [Mimic][mimic] to understand its use.
```sh
let _ =
Git_kv.connect ctx "git@github.com:mirage/mirage.git" >>= fun t ->
...
```
The user can manipulate the repository as an [RW][mirage-kv-rw] repository. Any
change to the repository requires a new commit. These changes can be sent to
the remote repository by deriving manipulation functions with the `and_push`
suffix:
```ocaml
module Store = Git_kv.Make (Pclock)
let new_file_locally t =
Store.set t Mirage_kv.Key.(empty / "foo") "foo" >>= fun () ->
...
let new_file_locally_and_remotely t =
Git_kv.pull t >>= fun _diff ->
Store.set_and_push t Mirage_kv.Key.(empty / "foo") "foo" >>= fun () ->
...
```
[mimic]: https://dinosaure.github.io/mimic/mimic/index.html
[mirage-kv-rw]: https://github.com/mirage/mirage-kv