This is a from scratch implementation of the reftable format for storing Git ref and reflog data.

The spec is at https://eclipse.googlesource.com/jgit/jgit/+/refs/heads/master/Documentation/technical/reftable.md

Based on the implementation, there is also a proposal for a v2 of the format.

Java

Reftable was originally implemented in JGit, and can be considered the reference implementation. The code has two parts:

• The format itself: https://eclipse.googlesource.com/jgit/jgit/+/master/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable

• The layout within a local disk repository: https://gerrit.googlesource.com/jgit/+/master/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileReftableStack.java

GO

The Go implementation implements the spec completely. API doc.

C

An experimental implementation in C is under the directory c/ . It is functionally equivalent to the Go version. Build and test it using

bazel test c/...

API is documented in side the reftable.h header.

It includes a fragment of the zlib library to provide uncompress2(), which is a recent addition to the API. zlib is licensed as follows:

 (C) 1995-2017 Jean-loup Gailly and Mark Adler

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

  Jean-loup Gailly        Mark Adler
  jloup@gzip.org          madler@alumni.caltech.edu

Background reading

• Spec: https://github.com/eclipse/jgit/blob/master/Documentation/technical/reftable.md

• Original discussion on JGit-dev: https://www.eclipse.org/lists/jgit-dev/msg03389.html

• First design discussion on git@vger: https://public-inbox.org/git/CAJo=hJtyof=HRy=2sLP0ng0uZ4=S-DpZ5dR1aF+VHVETKG20OQ@mail.gmail.com/

• Last design discussion on git@vger: https://public-inbox.org/git/CAJo=hJsZcAM9sipdVr7TMD-FD2V2W6_pvMQ791EGCDsDkQ033w@mail.gmail.com/

• First attempt at implementation: https://public-inbox.org/git/CAP8UFD0PPZSjBnxCA7ez91vBuatcHKQ+JUWvTD1iHcXzPBjPBg@mail.gmail.com/

• libgit2 support issue: https://github.com/libgit2/libgit2/issues

• GitLab support issue: https://gitlab.com/gitlab-org/git/issues/6

• go-git support issue: https://github.com/src-d/go-git/issues/1059

DISCLAIMER

This is not an official Google product