DataLad

Overview

DataLad is a data management layer over Git and git-annex. Git tracks the dataset structure, small text files, and the history. git-annex tracks the content of large files, storing each file as a key and keeping the bytes somewhere that is not necessarily the local repository.

A normal clone retrieves Git history and the top-level file listing while leaving annexed bytes unfetched. Installed subdatasets have their own histories; a clone does not automatically populate them. Clone cost depends on Git history and file count, not just the data volume. Retrieve annexed bytes selectively with datalad get.

The second thing DataLad adds is provenance. datalad run executes a command and commits the result together with a machine-readable record of the command, its inputs, and its outputs. datalad rerun reads that record back and re-executes it. This turns "how was this figure produced" from an archaeology problem into a command.