Datalad Diff

Skill: datalad-diff

Compare file-level state between two points in a DataLad dataset's history. datalad diff reports which files changed and their annex state transitions — it does not show line-level content diffs.

Steps

1. Verify DataLad context — check for .datalad/ in the current directory or any

parent: ``bash ls .datalad/ 2>/dev/null || git rev-parse --show-toplevel ``

• Dataset found: continue.
• No dataset found: inform the user; suggest plain git diff for non-DataLad repos.

1. Determine the comparison scope — read $ARGUMENTS and conversation context to

identify what the user wants to compare. Map to one of these forms:

| User intent | Command form | |-------------|-------------| | Working tree vs last commit | datalad diff (no args) | | Working tree vs specific commit | datalad diff --from | | Two specific commits | datalad diff --from --to | | Named revision (branch, tag) | datalad diff --from |

If the scope is ambiguous, ask the user: > "Are you comparing the current working tree to HEAD, or two specific commits? > If comparing commits, please provide the commit hashes or branch names."

1. Construct and run the diff command:

``bash datalad diff [--from ] [--to ] [paths...] `` Show the command before running it. Present the full output to the user.

1. Interpret the output — explain the change types shown:

| Type | Meaning | |------|---------| | added | File did not exist in the earlier revision; exists in the later one | | deleted | File existed in the earlier revision; removed in the later one | | modified | File content changed between revisions | | untracked | File is present locally but outside the compared revision range |

For annexed files, note that datalad diff reports pointer-level changes (key changed), not byte-level diffs.

1. Clarify line-level diffs if asked — datalad diff is file-level only. If the

user needs to see line-by-line content changes, point them to: ``bash git diff -- ` This works for git-tracked files; annexed file content must be retrieved first with datalad get before git diff` can show it.

Constraints

• Read-only — never stage, commit, or modify any file.
• Always show the constructed command before running it.
• Always explain that datalad diff is file-level, not line-level, and direct the user

to git diff when they need line-level comparisons.

• If the user provides only one hash/ref, treat it as --from (compare that ref to the

current working tree) and confirm this interpretation before running.

• Do not use git diff as a substitute — datalad diff correctly handles annexed file

pointers and subdataset boundaries.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: neuroanalytics
• Source: neuroanalytics/data-science-harness
• License: MIT

Install and usage instructions live in the source repository linked above.