Automatically generate change logs on release (#18401)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

.gemini/skills/docs-changelog/SKILL.md

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+---
+name: docs-changelog
+description: Provides a step-by-step procedure for generating Gemini CLI changelog files based on github release information.
+---
+
+# Procedure: Updating Changelog for New Releases
+
+The following instructions are run by Gemini CLI when processing new releases.
+
+## Objective
+
+To standardize the process of updating the Gemini CLI changelog files for a new
+release, ensuring accuracy, consistency, and adherence to project style
+guidelines.
+
+## Release Types
+
+This skill covers two types of releases:
+
+*   **Standard Releases:** Regular, versioned releases that are announced to all
+    users. These updates modify `docs/changelogs/latest.md` and
+    `docs/changelogs/index.md`.
+*   **Preview Releases:** Pre-release versions for testing and feedback. These
+    updates only modify `docs/changelogs/preview.md`.
+
+Ignore all other releases, such as nightly releases.
+
+### Expected Inputs
+
+Regardless of the type of release, the following information is expected:
+
+*   **New version number:** The version number for the new release
+    (e.g., `v0.27.0`).
+*   **Release date:** The date of the new release (e.g., `2026-02-03`).
+*   **Raw changelog data:** A list of all pull requests and changes
+    included in the release, in the format `description by @author in
+    #pr_number`.
+*   **Previous version number:** The version number of the last release can be
+    calculated by decreasing the minor version number by one and setting the
+    patch or bug fix version number.
+
+## Procedure
+
+### Initial Setup
+
+1.  Identify the files to be modified: 
+
+    For standard releases, update `docs/changelogs/latest.md` and
+    `docs/changelogs/index.md`. For preview releases, update
+    `docs/changelogs/preview.md`.
+
+2.  Activate the `docs-writer` skill.
+
+### Analyze Raw Changelog Data
+
+1.  Review the complete list of changes. If it is a patch or a bug fix with few
+    changes, skip to the "Update `docs/changelogs/latest.md` or
+    `docs/changelogs/preview.md`" section.
+
+2.  Group related changes into high-level categories such as
+    important features, "UI/UX Improvements", and "Bug Fixes". Use the existing
+    announcements in `docs/changelogs/index.md` as an example.
+
+### Create Highlight Summaries
+
+Create two distinct versions of the release highlights.
+
+**Important:** Carefully inspect highlights for "experimental" or
+"preview" features before public announcement, and do not include them.
+
+#### Version 1: Comprehensive Highlights (for `latest.md` or `preview.md`)
+
+Write a detailed summary for each category focusing on user-facing
+impact.
+
+#### Version 2: Concise Highlights (for `index.md`)
+
+Skip this step for preview releases.
+
+Write concise summaries including the primary PR and author
+(e.g., `([#12345](link) by @author)`).
+
+### Update `docs/changelogs/latest.md` or `docs/changelogs/preview.md`
+
+1. Read current content and use `write_file` to replace it with the new
+  version number, and date.
+  
+  If it is a patch or bug fix with few changes, simply add these
+  changes to the "What's Changed" list. Otherwise, replace comprehensive
+  highlights, and the full "What's Changed" list. 
+
+2. For each item in the "What's Changed" list, keep usernames in plaintext, and
+  add github links for each issue number. Example:
+
+  "- feat: implement /rewind command by @username in
+  [#12345](https://github.com/google-gemini/gemini-cli/pull/12345)"
+
+3. Skip entries by @gemini-cli-robot.
+
+4. Do not add the "New Contributors" section.
+
+5. Update the "Full changelog:" link with the previous version and the new
+version, unless it is a patch or a bug fix, in which case simply update the
+link's new version and keep the previous version the same.
+
+6. Ensure lines are wrapped to 80 characters.
+
+### Update `docs/changelogs/index.md`
+
+Skip this step for patches, bug fixes, or preview releases.
+
+Insert a new "Announcements" section for the new version directly
+above the previous version's section. Ensure lines are wrapped to
+80 characters.
+
+### Finalize
+
+Run `npm run format` to ensure consistency.

.github/workflows/release-notes.yml

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+# This workflow is triggered on every new release.
+# It uses Gemini to generate release notes and creates a PR with the changes.
+name: 'Generate Release Notes'
+
+on:
+  release:
+    types: ['created']
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'New version (e.g., v1.2.3)'
+        required: true
+        type: 'string'
+      body:
+        description: 'Release notes body'
+        required: true
+        type: 'string'
+      time:
+        description: 'Release time'
+        required: true
+        type: 'string'
+
+jobs:
+  generate-release-notes:
+    runs-on: 'ubuntu-latest'
+    permissions:
+      contents: 'write'
+      pull-requests: 'write'
+    steps:
+      - name: 'Checkout repository'
+        uses: 'actions/checkout@v4'
+        with:
+          # The user-level skills need to be available to the workflow
+          fetch-depth: 0
+
+      - name: 'Set up Node.js'
+        uses: 'actions/setup-node@v4'
+        with:
+          node-version: '20'
+
+      - name: 'Get release information'
+        id: 'release_info'
+        run: |
+          VERSION="${{ github.event.inputs.version || github.event.release.tag_name }}"
+          BODY="${{ github.event.inputs.body || github.event.release.body }}"
+          TIME="${{ github.event.inputs.time || github.event.release.created_at }}"
+
+          echo "VERSION=${VERSION}" >> "$GITHUB_OUTPUT"
+          echo "TIME=${TIME}" >> "$GITHUB_OUTPUT"
+
+          # Use a heredoc to preserve multiline release body
+          echo 'RAW_CHANGELOG<<EOF' >> "$GITHUB_OUTPUT"
+          echo "${BODY}" >> "$GITHUB_OUTPUT"
+          echo 'EOF' >> "$GITHUB_OUTPUT"
+        env:
+          GH_TOKEN: '${{ secrets.GITHUB_TOKEN }}'
+
+      - name: 'Generate Changelog with Gemini'
+        uses: 'google-github-actions/run-gemini-cli@a3bf79042542528e91937b3a3a6fbc4967ee3c31' # ratchet:google-github-actions/run-gemini-cli@v0
+        env:
+          VERSION: '${{ steps.release_info.outputs.VERSION }}'
+          RAW_CHANGELOG: '${{ steps.release_info.outputs.RAW_CHANGELOG }}'
+        with:
+          gemini_api_key: '${{ secrets.GEMINI_API_KEY }}'
+          prompt: |
+            Activate the 'docs-changelog' skill.
+
+            **Release Information:**
+            - New Version: $VERSION
+            - Release Date: $TIME
+            - Raw Changelog Data: $RAW_CHANGELOG
+
+            Execute the release notes generation process using the information provided.
+
+      - name: 'Create Pull Request'
+        uses: 'peter-evans/create-pull-request@v6'
+        with:
+          token: '${{ secrets.GITHUB_TOKEN }}'
+          commit-message: 'docs(changelog): update for ${{ steps.release_info.outputs.VERSION }}'
+          title: 'Changelog for ${{ steps.release_info.outputs.VERSION }}'
+          body: |
+            This PR contains the auto-generated changelog for the ${{ steps.release_info.outputs.VERSION }} release.
+
+            Please review and merge.
+          branch: 'changelog-${{ steps.release_info.outputs.VERSION }}'
+          delete-branch: true