| 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.
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
Step 2 — Compare against origin/main
Run:
git diff origin/main...HEAD
Step 3 — Compare against origin/master
Run:
git diff origin/master...HEAD
Failure Condition
If ALL of the above steps either error or produce empty output:
Return:
diff_source_command = nulldiff_context = ""error = "NO_DIFF_FOUND"
Do not guess.
Do not fabricate changes.
Do not continue silently.
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".
Guarantees
This skill guarantees:
- Deterministic fallback order
- No hallucinated diffs
- Explicit failure signaling
- Compatibility with strict JSON-only agents
