pr-update

name	PR: Update
description	{{ ƔƔƔ }} Update a PR description to account for commits made since it was last written
when_to_use	When new commits landed on a branch after its PR was opened and the description no longer reflects the full diff.
model	sonnet
disable-model-invocation	true
allowed-tools	["Bash(git:*)","Bash(gh:*)","Read","Glob","Grep"]
argument-hint	<pr-number>

Update an Existing PR

Update the description of PR #$ARGUMENTS.

Steps

1. Fetch current PR state

Run:

gh pr view $ARGUMENTS --json body,title,headRefName,baseRefName

2. Find the watermark

Look in the PR body for a comment in this exact format:

<!-- pr-update-watermark: <commit-sha> -->

If found, note the SHA — this is where the last update stopped. Call it $WATERMARK_SHA.

If not found, treat the entire commit history on the branch as new.

3. Get new commits

Run:

git log <baseRefName>..<headRefName> --oneline

If a watermark was found, filter to only commits after $WATERMARK_SHA:

git log ${WATERMARK_SHA}..HEAD --oneline

If there are no new commits since the watermark, tell me and stop — the description is already up to date.

4. Analyse the new commits

For each new commit, run:

git show <sha> --stat

Understand what changed and why. Group related commits into coherent change categories.

5. Produce the updated PR body

Take the existing PR body and update it:

• Do not rewrite from scratch. Preserve existing content unless it is now inaccurate.
• The body structure follows ~/.claude/library/templates/pr-description.md (the same template pr-create fills) — keep updates within that structure rather than adding new top-level sections.
• Update the ## Changes section to incorporate the new commits. If collapsible <details> blocks already exist, add new entries or update existing ones as appropriate.
• If the description references behaviour that has changed, correct it.
• Insert or replace the watermark comment at the very end of the body, using the SHA of the most recent commit on the branch:

<!-- pr-update-watermark: <latest-sha> -->

6. Show me the diff

Display:

• The updated PR body in full
• A brief summary of what changed vs the previous description

Wait for my approval.

7. Apply the update

Once approved, run:

gh pr edit $ARGUMENTS --body "<updated body>"

Confirm success.