uniondiff - Directory difference calculator

uniondiff is a simple tool for calculating the directory difference between two directories or archives. uniondiff performs the calculation below:

upper = merged - lower

This tool acts as the inverse union mount file systems. Whereas typically you combine a lower and upper directory to produce a merged directory, uniondiff takes as input the merged directory and subtracts out the lower directory to produce the upper directory. In particular, the resulting output can be mounted as the upper directory along with the lower to produce the original merged directory.

uniondiff is intended for use with low level file system tools (e.g. container systems) or for simply storing diffs of directories. Note that this tool does not store compact diffs of individual files; a file will appear in full in the diff iff its content or metadata has changed between the merged and lower operands.

Installation

uniondiff can be installed through pip. This installs both the uniondiff CLI utility and the uniondiff Python library.

pip install uniondiff

uniondiff is supported and tested on Python 3.11-3.15

Examples

Compute the directory difference between the directory "data-day10" and "data-day9". By default the output will be written as a tar file.

uniondiff data-day10 data-day9 > diff.tar

uniondiff can also write directly to the file system. Note that it will ignore ownership changes unless you also pass the --preserve-owners flag.

uniondiff data-day10 data-day9 --output-type file -o diff

You can also use tar archives as the input paths.

uniondiff data-day10.tar data-day9.tgz > diff.tar

Contributing

If you want to contribute to uniondiff, you can do so by creating a pull request. lease make sure to include a detailed description of the changes you're proposing.