[IzumiSy]

Motivation

Publishing follow-up changes to an existing PR requires staging and committing local changes, pushing them to the correct branch, and keeping the PR description accurate. The existing create-pr skill covers initial PR creation, but not this recurring workflow. Add a dedicated skill so these steps can be requested together without creating a duplicate PR, while honoring explicit limits on which changes to publish.

Design Decision

Separate creation from updates

Keep update-pr focused on existing open PRs and reuse create-pr's Git safety rules, confidentiality rules, and GitHub tooling policy. This keeps the two workflows distinct without introducing a script or duplicating their shared policies.

Use the right scope for each operation

By default, review both staged and unstaged changes, then stage tracked changes with git add -u, including the remaining edits in partially staged files. Honor staged-only or narrower requests and leave untracked files untouched unless explicitly included. Use the reviewed staged diff as the source of truth for the new commit and the full published PR diff for its description. Cymbal provides optional change-impact context, but does not determine what gets committed or published.

Share the description format within the Pi package

Move the existing description template and writing rules into skills/references/pr-description.md, which both PR skills read directly. These skills are intended for use together in this Pi package, so a package-local shared reference avoids template drift without duplicating files or adding a generation step. Keep creation-specific behavior, including the Draft default, in create-pr.

Summary

• Add an update-pr skill covering target verification, staging tracked changes, commits, explicit pushes, whole-PR description updates, and partial-failure reporting.
• Honor explicit publication scope, preserve excluded changes and existing PR metadata, and guard against incorrect fork destinations, protected branches, and unintended publication of pre-existing unpushed commits.
• Extract the existing Motivation / optional Design Decision / Summary template and writing rules into a shared reference used by both PR skills.
• Document /skill:update-pr, its requirements, and bundled shared skill references in the README.