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tar-diff

tar-diff is a golang library and set of commandline tools to diff and patch tar files.

pkg/tar-diff and the tar-diff takes two (optionally compressed) tar files and generates a single file representing the delta between them.

pkg/tar-patch takes a tardiff and the uncompressed contents (such as an extracted directory) of the first tarfile and reconstructs (binary identically) the second tarfile (uncompressed).

Example:

$ tar-diff old.tar.gz new.tar.gz delta.tardiff
$ tar xf old.tar.gz -C extracted/
$ tar-patch delta.tardiff extracted/ reconstructed.tar
$ zcat new.tar.gz | shasum
$ shasum reconstructed.tar

The main usecase for tar-diff is for more efficient distribution of OCI images. These images are typically transferred as compressed tar files, but the content is refered to and validated by the checksum of the uncomressed content. This makes it possible to use an extracted earlier version of and image in combination with a tardiff to reconstruct and validate the current version of the image.

Delta compression is based on bsdiff and zstd compression.

The tar-diff file-format is described in file-format.md

License

tar-diff is licensed under the Apache License, Version 2.0. See LICENSE for the full license text.