Switch changelog handling to fragments

.changes/archive/.gitkeep

@@ -0,0 +1 @@
+

.changes/unreleased/.gitkeep

@@ -0,0 +1 @@
+

.github/workflows/changelog-fragment-draft.yml

@@ -0,0 +1,222 @@
+name: Draft changelog fragment
+
+on:
+  pull_request_target:
+    branches:
+      - main
+      - next
+    types: [opened, reopened, synchronize, labeled, unlabeled]
+
+permissions:
+  models: read
+  pull-requests: write
+
+concurrency:
+  group: "${{ github.workflow }}-${{ github.event.pull_request.number }}"
+  cancel-in-progress: true
+
+jobs:
+  draft:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Collect PR context
+        id: context
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const fs = require('fs');
+            const path = require('path');
+
+            const pr = context.payload.pull_request;
+            const owner = context.repo.owner;
+            const repo = context.repo.repo;
+            const files = await github.paginate(github.rest.pulls.listFiles, {
+              owner,
+              repo,
+              pull_number: pr.number,
+              per_page: 100,
+            });
+
+            const hasNoChangelog = (pr.labels || []).some(label => label.name === 'no changelog');
+            const hasFragment = files.some(file => /^\.changes\/unreleased\/.+\.md$/.test(file.filename));
+            const shouldRun = !hasNoChangelog && !hasFragment;
+
+            const changedFiles = files.map(file => file.filename).join('\n') || '(no changed files reported)';
+
+            const diffSections = [];
+            let totalChars = 0;
+            for (const file of files) {
+              const patch = file.patch || '[diff omitted by GitHub]';
+              const truncatedPatch = patch.length > 4000 ? `${patch.slice(0, 4000)}\n...[truncated]` : patch;
+              const section = `### ${file.filename}\n${truncatedPatch}`;
+              if (totalChars + section.length > 20000) {
+                diffSections.push('...[additional diff omitted]');
+                break;
+              }
+              diffSections.push(section);
+              totalChars += section.length;
+            }
+
+            const tempDir = process.env.RUNNER_TEMP;
+            const inputsDir = path.join(tempDir, 'changelog-fragment-inputs');
+            fs.mkdirSync(inputsDir, { recursive: true });
+
+            const bodyPath = path.join(inputsDir, 'body.txt');
+            const titlePath = path.join(inputsDir, 'title.txt');
+            const changedFilesPath = path.join(inputsDir, 'changed_files.txt');
+            const diffPath = path.join(inputsDir, 'diff.txt');
+            const promptPath = path.join(inputsDir, 'prompt.prompt.yml');
+
+            fs.writeFileSync(bodyPath, pr.body || '');
+            fs.writeFileSync(titlePath, pr.title || '');
+            fs.writeFileSync(changedFilesPath, changedFiles);
+            fs.writeFileSync(diffPath, diffSections.join('\n\n'));
+            fs.writeFileSync(promptPath, `messages:
+              - role: system
+                content: |-
+                  You draft changelog fragments for a Rust workspace.
+                  Return JSON only.
+                  Pick the smallest accurate kind from: breaking, change, enhancement, fix.
+                  Write a single concise, user-facing summary sentence.
+                  Do not mention tests, reviews, CI, or implementation details unless they matter to users.
+                  Only set crate when a single obvious crate is central to the change; otherwise use an empty string.
+              - role: user
+                content: |-
+                  Draft a changelog fragment from this pull request.
+
+                  Pull request URL:
+                  {{pr_url}}
+
+                  Pull request title:
+                  {{title}}
+
+                  Pull request body:
+                  {{body}}
+
+                  Changed files:
+                  {{changed_files}}
+
+                  Unified diff:
+                  {{diff}}
+            model: openai/gpt-4.1-mini
+            responseFormat: json_schema
+            jsonSchema: |-
+              {
+                "name": "changelog_fragment",
+                "strict": true,
+                "schema": {
+                  "type": "object",
+                  "properties": {
+                    "kind": {
+                      "type": "string",
+                      "enum": ["breaking", "change", "enhancement", "fix"]
+                    },
+                    "crate": {
+                      "type": "string"
+                    },
+                    "summary": {
+                      "type": "string"
+                    }
+                  },
+                  "required": ["kind", "crate", "summary"],
+                  "additionalProperties": false
+                }
+              }
+            modelParameters:
+              temperature: 0.2
+              maxCompletionTokens: 250
+            `);
+
+            core.setOutput('should_run', shouldRun ? 'true' : 'false');
+            core.setOutput('pr_number', String(pr.number));
+            core.setOutput('pr_url', pr.html_url);
+            core.setOutput('body_path', bodyPath);
+            core.setOutput('title_path', titlePath);
+            core.setOutput('changed_files_path', changedFilesPath);
+            core.setOutput('diff_path', diffPath);
+            core.setOutput('prompt_path', promptPath);
+
+      - name: Run AI inference
+        if: ${{ steps.context.outputs.should_run == 'true' }}
+        id: inference
+        uses: actions/ai-inference@v1
+        with:
+          prompt-file: ${{ steps.context.outputs.prompt_path }}
+          input: |
+            pr_url: ${{ steps.context.outputs.pr_url }}
+          file_input: |
+            title: ${{ steps.context.outputs.title_path }}
+            body: ${{ steps.context.outputs.body_path }}
+            changed_files: ${{ steps.context.outputs.changed_files_path }}
+            diff: ${{ steps.context.outputs.diff_path }}
+
+      - name: Comment fragment instructions
+        if: ${{ steps.context.outputs.should_run == 'true' }}
+        env:
+          PR_NUMBER: ${{ steps.context.outputs.pr_number }}
+          PR_URL: ${{ steps.context.outputs.pr_url }}
+          RESPONSE_FILE: ${{ steps.inference.outputs.response-file }}
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const fs = require('fs');
+            const prNumber = process.env.PR_NUMBER;
+            const prUrl = process.env.PR_URL;
+            const response = JSON.parse(fs.readFileSync(process.env.RESPONSE_FILE, 'utf8'));
+            const marker = '<!-- changelog-fragment-draft -->';
+            const kind = response.kind;
+            const crate = response.crate || '';
+            const summary = response.summary;
+            const repoFragmentPath = `.changes/unreleased/${prNumber}.${kind}.md`;
+
+            const frontMatter = [
+              '---',
+              `kind: ${kind}`,
+              `pr: ${prUrl}`,
+              ...(crate ? [`crate: ${crate}`] : []),
+              '---',
+              '',
+              summary,
+            ];
+            const fragment = frontMatter.join('\n');
+            const body = [
+              marker,
+              'This pull request does not include a changelog fragment and is not labeled `no changelog`.',
+              '',
+              `Please add a file at \`${repoFragmentPath}\` with content like:`,
+              '',
+              '```md',
+              fragment,
+              '```',
+              '',
+              'If no changelog entry is needed, ask a maintainer to apply the `no changelog` label.',
+            ].join('\n');
+
+            const { owner, repo } = context.repo;
+            const issue_number = context.payload.pull_request.number;
+            const comments = await github.paginate(github.rest.issues.listComments, {
+              owner,
+              repo,
+              issue_number,
+              per_page: 100,
+            });
+
+            const existing = comments.find(comment =>
+              comment.user?.login === 'github-actions[bot]' && comment.body?.includes(marker)
+            );
+
+            if (existing) {
+              await github.rest.issues.updateComment({
+                owner,
+                repo,
+                comment_id: existing.id,
+                body,
+              });
+            } else {
+              await github.rest.issues.createComment({
+                owner,
+                repo,
+                issue_number,
+                body,
+              });
+            }

.github/workflows/changelog-release.yml

@@ -0,0 +1,46 @@
+name: Prepare changelog release
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: Release version, e.g. 0.23.0
+        required: true
+        type: string
+      date:
+        description: Release date in YYYY-MM-DD format. Defaults to today if empty.
+        required: false
+        type: string
+
+permissions:
+  contents: write
+
+jobs:
+  prepare:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Prepare changelog release
+        run: |
+          if [ -n "${{ inputs.date }}" ]; then
+            ./scripts/prepare-changelog-release.py --version "${{ inputs.version }}" --date "${{ inputs.date }}"
+          else
+            ./scripts/prepare-changelog-release.py --version "${{ inputs.version }}"
+          fi
+
+      - name: Commit prepared changelog
+        run: |
+          if git diff --quiet -- CHANGELOG.md .changes; then
+            echo "No changelog changes were produced."
+            exit 1
+          fi
+
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add CHANGELOG.md .changes
+          git commit -m "chore(changelog): prepare ${{ inputs.version }}"
+          git push

.github/workflows/changelog.yml

@@ -1,5 +1,4 @@
 # Runs changelog related jobs.
-# CI job heavily inspired by: https://github.com/tarides/changelog-check-action
 
 name: changelog
 
@@ -25,5 +24,5 @@ jobs:
         env:
           BASE_REF: ${{ github.event.pull_request.base.ref }}
           NO_CHANGELOG_LABEL: ${{ contains(github.event.pull_request.labels.*.name, 'no changelog') }}
-        run: ./scripts/check-changelog.sh "${{ inputs.changelog }}"
+        run: ./scripts/check-changelog.sh
         shell: bash

scripts/check-changelog.sh

@@ -1,21 +1,35 @@
 #!/bin/bash
-set -uo pipefail
+set -euo pipefail
 
-CHANGELOG_FILE="${1:-CHANGELOG.md}"
+FRAGMENT_GLOB=':(glob).changes/unreleased/*.md'
 
-if [ "${NO_CHANGELOG_LABEL}" = "true" ]; then
-    # 'no changelog' set, so finish successfully
+if [[ "${NO_CHANGELOG_LABEL:-false}" == "true" ]]; then
     echo "\"no changelog\" label has been set"
     exit 0
-else
-    # a changelog check is required
-    # fail if the diff is empty
-    if git diff --exit-code "origin/${BASE_REF}" -- "${CHANGELOG_FILE}"; then
-        >&2 echo "Changes should come with an entry in the \"CHANGELOG.md\" file. This behavior
-can be overridden by using the \"no changelog\" label, which is used for changes
-that are trivial / explicitly stated not to require a changelog entry."
-        exit 1
-    fi
+fi
+
+if [[ -z "${BASE_REF:-}" ]]; then
+    echo "BASE_REF must be set" >&2
+    exit 1
+fi
 
-    echo "The \"CHANGELOG.md\" file has been updated."
+fragments=()
+while IFS= read -r fragment; do
+    [[ -n "$fragment" ]] && fragments+=("$fragment")
+done < <(git diff --name-only --diff-filter=AMR "origin/${BASE_REF}...HEAD" -- "$FRAGMENT_GLOB")
+
+if [[ "${#fragments[@]}" -eq 0 ]]; then
+    cat >&2 <<'EOF'
+Changes should come with a changelog fragment in ".changes/unreleased/".
+This behavior can be overridden by using the "no changelog" label for changes
+that are trivial or explicitly stated not to require a changelog entry.
+EOF
+    exit 1
 fi
+
+validate_args=()
+for fragment in "${fragments[@]}"; do
+    validate_args+=(--validate-fragment "$fragment")
+done
+
+./scripts/prepare-changelog-release.py "${validate_args[@]}"