Add release automation

.github/workflows/build.yaml

@@ -1,21 +1,25 @@
-name: Build LaTeX documents
-
+name: Build PDF documents
 on:
+  workflow_call:
   pull_request:
     branches:
       - trunk
+  push:
+    tags:
+      - v*
 
 jobs:
-  build_latex:
+  build_pdf:
+    runs-on: ubuntu-latest
     strategy:
       matrix:
         name:
           - dotted
           - gridded
-    runs-on: ubuntu-latest
     steps:
       - name: Set up Git repository
         uses: actions/checkout@v2
+
       - name: Compile LaTeX documents
         uses: xu-cheng/latex-action@v2
         with:
@@ -28,7 +32,37 @@ jobs:
           root_file: license.tex
           latexmk_use_xelatex: true
           post_compile: pdfjam --vanilla --noautoscale true --outfile ${{ matrix.name }}.pdf ${{ matrix.name }}-booklet.pdf license.pdf
+
       - uses: actions/upload-artifact@v2
         with:
-          name: ${{ matrix.name }}
           path: ${{ matrix.name }}.pdf
+
+  release:
+    if: startsWith(github.ref, 'refs/tags/v')
+    needs: build_pdf
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Set up Git repository
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: "0"
+
+      - name: Download artifacts
+        uses: actions/download-artifact@v2
+
+      - name: Build changelog
+        id: build_changelog
+        uses: mikepenz/release-changelog-builder-action@v2
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Create Release
+        uses: ncipollo/release-action@v1
+        with:
+          artifacts: "artifact/*"
+          body: ${{ steps.build_changelog.outputs.changelog }}
+          token: ${{ secrets.GITHUB_TOKEN }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}