git-changes-context

name	git-changes-context
description	Reliably obtain a non-empty unified git diff for the current branch using safe fallbacks (origin/HEAD...HEAD, origin/main...HEAD, origin/master...HEAD) and return structured JSON containing the diff and the command used.

Git Changes Context Skill

Purpose

Provide a deterministic way to obtain the actual change set (unified diff) for use by other agents (code review, security audit, test analysis, etc).

This skill MUST be used whenever a task depends on reviewing changes.

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Procedure

Follow these steps strictly and in order.

Important: You MUST attempt every step below until you find a non-empty diff. Do not return NO_DIFF_FOUND after running only one command.

For each step:

• Run the command exactly as written.
• If the command errors or produces empty output, proceed to the next step.
• If output is non-empty, set diff_source_command to the exact command string, set diff_context to the raw unified diff, and stop.

Step 1 — Compare against origin/HEAD (preferred default-branch fallback)

Run:

git diff origin/HEAD...HEAD

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Step 2 — Compare against origin/main

Run:

git diff origin/main...HEAD

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Step 3 — Compare against origin/master

Run:

git diff origin/master...HEAD

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Failure Condition

If ALL of the above steps either error or produce empty output:

Return:

• diff_source_command = null
• diff_context = ""
• error = "NO_DIFF_FOUND"

Do not guess. Do not fabricate changes. Do not continue silently.

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Output Contract (STRICT)

You MUST return JSON only.

Return exactly this shape:

{ "diff_source_command": string | null, "diff_context": string, "error": string | null }

Rules:

• No commentary.
• No markdown.
• No explanations.
• No additional keys.
• diff_context must contain raw unified diff text.
• If no diff found, error must be "NO_DIFF_FOUND".

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Guarantees

This skill guarantees:

• Deterministic fallback order
• No hallucinated diffs
• Explicit failure signaling
• Compatibility with strict JSON-only agents