Automate publishing new releases on crates.io

These scripts will help automate the steps required to publish new
releases on crates.io:

- update version number in `Cargo.toml`, `README.md`, and `src/lib.rs`

- update changelog in `README.md`

- run `cargo publish` if all tests pass

.github/workflows/prepare-release.yml

@@ -0,0 +1,153 @@
+name: Prepare Release PR
+
+on:
+  push:
+    branches:
+      - 'release-*'
+
+jobs:
+  setup:
+    runs-on: ubuntu-latest
+    outputs:
+      name: ${{ steps.vars.outputs.name }}
+      old-version: ${{ steps.vars.outputs.old-version }}
+      new-version: ${{ steps.vars.outputs.new-version }}
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v2
+
+      - name: Set variables
+        id: vars
+        run: |
+          NAME=$(cargo metadata -q --no-deps | jq -r '.packages[0].name')
+          OLD_VERSION=$(cargo metadata -q --no-deps | jq -r '.packages[0].version')
+          NEW_VERSION=$(echo ${{ github.ref }} | cut -d '-' -f 2-)
+          echo "Version from Cargo:  $OLD_VERSION"
+          echo "Version from branch: $NEW_VERSION"
+
+          echo "::set-output name=name::$NAME"
+          echo "::set-output name=old-version::$OLD_VERSION"
+          echo "::set-output name=new-version::$NEW_VERSION"
+
+      - name: Verify version format
+        run: |
+          echo '${{ steps.vars.outputs.new-version }}' | grep -q '^[0-9]\+\.[0-9]\+\.[0-9]\+$'
+
+  pull-request:
+    needs: setup
+    if: ${{ needs.setup.outputs.old-version != needs.setup.outputs.new-version }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v2
+
+      - name: Configure Git user
+        run: |
+          git config user.name "Martin Geisler"
+          git config user.email "martin@geisler.net"
+
+      - name: Update changelog for version ${{ needs.setup.outputs.new-version }}
+        id: changelog
+        uses: actions/github-script@v2
+        with:
+          script: |
+            var fs = require('fs')
+            const old_version = '${{ needs.setup.outputs.old-version }}'
+            const new_version = '${{ needs.setup.outputs.new-version }}'
+
+            let cutoff = '1970-01-01'
+            const releases = await github.repos.listReleases(context.repo)
+            for (const release of releases.data) {
+              if (release.tag_name == old_version) {
+                cutoff = release.published_at
+                break
+              }
+            }
+            core.info(`Finding merged PRs after ${cutoff}`)
+
+            let q = [`repo:${context.repo.owner}/${context.repo.repo}`,
+                     'is:pr', 'is:merged', `merged:>${cutoff}`]
+            const prs = await github.search.issuesAndPullRequests({
+              q: q.join(' '),
+              sort: 'created',
+              order: 'asc',
+            })
+            core.info(`Found ${prs.data.items.length} merged PRs`)
+
+            const changelog = prs.data.items.map(
+              pr => `* [#${pr.number}](${pr.html_url}): ${pr.title}`
+            ).join('\n\n')
+            core.exportVariable('CHANGELOG', changelog)
+
+            var readme = fs.readFileSync('README.md', 'utf8')
+            const today = new Date().toISOString().split('T')[0]
+            const heading = `## Version ${new_version} (${today})\n`
+            if (readme.match('## Unreleased')) {
+              readme = readme.replace('## Unreleased', `${heading}\n${changelog}`)
+            } else {
+              readme = readme.replace('# Changelog', `# Changelog\n\n${heading}\n${changelog}`)
+            }
+            fs.writeFileSync('README.md', readme)
+
+      - name: Commit changelog
+        run: |
+          git commit --all -m "Update changelog for version ${{ needs.setup.outputs.new-version }}"
+
+      - name: Update TOML code blocks
+        run: |
+          import fileinput, re, sys
+
+          NAME = '${{ needs.setup.outputs.name }}'
+          NEW_VERSION = '${{ needs.setup.outputs.new-version }}'
+          MAJOR_MINOR = '.'.join(NEW_VERSION.split('.')[:2])
+
+          for line in fileinput.input(inplace=True):
+              line = re.sub(f'{NAME} = "[^"]+"',
+                            f'{NAME} = "{MAJOR_MINOR}"', line)
+              line = re.sub(f'{NAME} = {{ version = "[^"]+"',
+                            f'{NAME} = {{ version = "{MAJOR_MINOR}"', line)
+              sys.stdout.write(line)
+        shell: python3 {0} README.md
+
+      - name: Update html_root_url
+        run: |
+          import fileinput, re, sys
+
+          NAME = '${{ needs.setup.outputs.name }}'
+          NEW_VERSION = '${{ needs.setup.outputs.new-version }}'
+
+          for line in fileinput.input(inplace=True):
+              sys.stdout.write(
+                  re.sub(f'html_root_url = "https://docs.rs/{NAME}/[^"]+"',
+                         f'html_root_url = "https://docs.rs/{NAME}/{NEW_VERSION}"', line))
+        shell: python3 {0} src/lib.rs
+
+      - name: Update crate version to ${{ needs.setup.outputs.new-version }}
+        uses: thomaseizinger/set-crate-version@1.0.0
+        with:
+          version: ${{ needs.setup.outputs.new-version }}
+
+      - name: Build and test
+        run: |
+            cargo test
+
+      - name: Commit version bump
+        run: |
+          git commit --all -m "Bump version to ${{ needs.setup.outputs.new-version }}"
+
+      - name: Push version bump
+        run: git push origin
+
+      - name: Create pull request
+        uses: actions/github-script@v2
+        with:
+          script: |
+            const pr = await github.pulls.create({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              head: 'release-${{ needs.setup.outputs.new-version }}',
+              base: 'master',
+              title: 'Release ${{ needs.setup.outputs.new-version }}',
+              body: process.env.CHANGELOG,
+            })
+            core.info(`Created PR: ${pr.data.html_url}`)

.github/workflows/publish-crate.yml

@@ -0,0 +1,63 @@
+name: Publish Crate
+
+on:
+  push:
+    branches:
+      - master
+    paths:
+      - Cargo.toml
+  repository_dispatch:
+    types: publish
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v2
+
+      - name: Set variables
+        id: vars
+        run: |
+          NAME=$(cargo metadata -q --no-deps | jq -r '.packages[0].name')
+          VERSION=$(cargo metadata -q --no-deps | jq -r '.packages[0].version')
+          CHANGELOG=$(awk '/^## Version/ {i++}; i==1 {print}; i>1 {exit}' README.md \
+            | python3 -c 'import sys, json; print(json.dumps(sys.stdin.read()))')
+          echo "::set-output name=name::$NAME"
+          echo "::set-output name=version::$VERSION"
+          echo "::set-output name=changelog::$CHANGELOG"
+          echo "Found $NAME-$VERSION"
+
+      - name: Lookup ${{ steps.vars.outputs.version }} tag
+        id: need-release
+        uses: actions/github-script@v2
+        with:
+          script: |
+            const version = '${{ steps.vars.outputs.version }}'
+            const tags = await github.repos.listTags(context.repo)
+            if (tags.data.some(tag => tag.name == version)) {
+                core.info(`Found ${version} tag -- will skip publish step`)
+                return false
+            }
+            core.info(`Found no ${version} tag -- will proceed with publishing`)
+            return true
+
+      # The result from above is JSON-encoded, meaning that we
+      # end up with the string 'true', not the Boolean true.
+      - if: steps.need-release.outputs.result == 'true'
+        name: Publish crate to crates.io
+        run: |
+          echo "Publishing ${{ steps.vars.outputs.name }}-${{ steps.vars.outputs.version }}"
+          cargo publish --token ${{ secrets.CARGO_TOKEN }}
+
+      - if: steps.need-release.outputs.result == 'true'
+        name: Create GitHub release
+        uses: actions/create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          tag_name: ${{ steps.vars.outputs.version }}
+          release_name: ${{ steps.vars.outputs.name }}-${{ steps.vars.outputs.version }}
+          body: ${{ fromJson(steps.vars.outputs.changelog) }}
+          draft: false
+          prerelease: false