tar-diff

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 tool take two (optionally compressed) tar files and generate a single file representing the delta between them (a tardiff file).

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

Build requirements

• golang >= 1.25 (see go.mod)
• make
• tar
• diffutils, bzip2, gzip (for tests)

Runtime dependencies

None. The built binaries are self-contained.

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