Generate changelog with semantic-release

.github/workflows/changelog.yml

@@ -0,0 +1,18 @@
+name: changelog
+on:
+  push:
+    branches:
+      - 'release-*'
+      - '*changelog*'
+jobs:
+  all:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@master
+      - uses: actions/setup-node@master
+        with:
+          node-version: 11
+      - name: install
+        run: npm install
+      - name: changelog
+        run: script/changelog.js

lib/semantic-release-plugin.js

@@ -0,0 +1,134 @@
+const Octokit = require('@octokit/rest')
+
+const commitMetadata = new Map()
+
+const noteGroups = {
+  breaking: {title: ':boom: Breaking changes'},
+  enhancement: {title: ':rocket: Enhancements'},
+  fix: {title: ':bug: Bug fixes'},
+  docs: {title: ':memo: Documentation'},
+  internal: {title: ':house: Internal'},
+  polish: {title: ':nail_care: Polish'}
+}
+
+const releaseLabels = {
+  'Tag: Breaking Change': {releaseType: 'major', group: 'breaking'},
+  'Tag: Enhancement': {releaseType: 'minor', group: 'enhancement'},
+  'Tag: Bug Fix': {releaseType: 'patch', group: 'fix'},
+  'Tag: Documentation': {releaseType: 'patch', group: 'docs'},
+  'Tag: Internal': {releaseType: 'patch', group: 'internal'},
+  'Tag: Polish': {releaseType: 'patch', group: 'polish'}
+}
+
+const repoContext = {owner: 'primer', repo: 'css'}
+const githubOptions = {
+  userAgent: '@primer/css changelog'
+}
+const {GITHUB_TOKEN} = process.env
+if (GITHUB_TOKEN) {
+  githubOptions.auth = GITHUB_TOKEN
+}
+
+const github = new Octokit(githubOptions)
+
+module.exports = {analyzeCommits, generateNotes}
+
+async function analyzeCommits(options, context) {
+  const {commits, logger} = context
+
+  const releaseTypes = new Map()
+
+  for (const commit of commits) {
+    const match = commit.message.match(/Merge pull request #(\d+)/)
+    if (match) {
+      const [, pullNumber] = match
+      logger.log(`Fetching PR #${pullNumber}...`)
+      // eslint-disable-next-line camelcase
+      const {data: pull} = await github.pulls.get(Object.assign({pull_number: pullNumber}, repoContext))
+
+      const labels = pull.labels.map(label => label.name)
+      if (labels.length) {
+        logger.log(`Got labels: "${labels.join('", "')}"`)
+        for (const label of labels) {
+          const {releaseType, group} = releaseLabels[label] || {}
+          if (releaseType) {
+            logger.info(`Label "${label}" matches release type: ${releaseType}`)
+
+            if (!releaseTypes.has(releaseType)) {
+              releaseTypes.set(releaseType, [])
+            }
+            releaseTypes.get(releaseType).push({pull, label})
+
+            commitMetadata.set(commit.hash, {pull, group})
+          }
+        }
+      }
+    } else {
+      logger.log(`No PR number found in commit: "${commit.message}"`)
+    }
+  }
+
+  let returnReleaseType
+
+  for (const releaseType of ['major', 'minor', 'patch']) {
+    if (releaseTypes.has(releaseType)) {
+      const pulls = releaseTypes.get(releaseType)
+      logger.info(`Found ${pulls.length} pulls for release type: ${releaseType}`)
+      for (const {pull, label} of pulls) {
+        logger.info(`- PR #${pull.number} labeled "${label}"`)
+        if (!returnReleaseType) {
+          returnReleaseType = releaseType
+        }
+      }
+    }
+  }
+
+  return returnReleaseType
+}
+
+async function generateNotes(options, context) {
+  const {
+    commits,
+    logger,
+    nextRelease: {version}
+  } = context
+
+  logger.info(`Finding metadata for ${commitMetadata.size} commits...`)
+  const releaseCommits = commits.map(commit => commitMetadata.get(commit.hash)).filter(Boolean)
+
+  if (releaseCommits.length) {
+    logger.info(`Got ${releaseCommits.length} release commits!`)
+
+    const groupItems = new Map()
+    const committers = new Set()
+    const {owner, repo} = repoContext
+    const baseURL = `https://github.com/${owner}/${repo}`
+    for (const {pull, group} of releaseCommits) {
+      if (!groupItems.has(group)) {
+        groupItems.set(group, [])
+      }
+      const {
+        number,
+        title,
+        user: {login}
+      } = pull
+      groupItems.get(group).push(`- [#${number}](${baseURL}/${number}) ${title}`)
+      committers.add(login)
+    }
+
+    return [
+      `## ${version}`,
+      ...Object.entries(noteGroups)
+        .filter(([group]) => groupItems.has(group))
+        .map(([group, {title}]) => `\n### ${title}\n${groupItems.get(group).join('\n')}`),
+      '',
+      `### Committers`,
+      ...Array.from(committers)
+        .sort()
+        .map(login => `- [@${login}](https://github.com/${login})`),
+      ''
+    ].join('\n')
+  } else {
+    logger.info(`No release commits. :(`)
+  }
+}