Add GitHub Action to automatically create a release when creating a tag

.github/workflows/create-release.yml

@@ -0,0 +1,59 @@
+name: Create release
+
+on:
+  create:
+    tags:
+
+jobs:
+  create-release:
+    if: github.event_name == 'create' && github.event.ref_type == 'tag'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check tag format
+        run: |
+          THIS_TAG="${GITHUB_REF#refs/tags/}"
+          if printf '%s' "$THIS_TAG" | grep -Eq '^[0-9]+\.[0-9]+\.[0-9]+$'; then
+            printf 'Tag %s is version-like\n' "$THIS_TAG"
+          else
+            printf 'Tag %s is not version-like\n' "$THIS_TAG"
+            THIS_TAG=
+          fi
+          printf 'THIS_TAG=%s\n' "$THIS_TAG" >> "$GITHUB_ENV"
+      - name: Checkout
+        if: env.THIS_TAG != ''
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+      - name: Extract release notes
+        if: env.THIS_TAG != ''
+        run: |
+          printf 'Generating release notes for tag %s\n' "$THIS_TAG"
+          TAGS="$(git tag --list --sort=-version:refname)"
+          PREVIOUS_TAG=
+          for TAG in $(git tag --list --sort=-version:refname); do
+            if test "$THIS_TAG" != "$TAG" && printf '%s' "$TAG" | grep -Eq '^[0-9]+\.[0-9]+\.[0-9]+$'; then
+              PREVIOUS_TAG="$TAG"
+              break
+            fi
+          done
+          if test -z "$PREVIOUS_TAG"; then
+            echo 'No previous tag found'
+            RELEASE_NOTES='First version'
+          else
+            printf 'Generating release notes for commits between %s and %s\n' "$PREVIOUS_TAG" "$THIS_TAG"
+            RELEASE_NOTES="$(git log --format='- %s' --no-merges --reverse "$PREVIOUS_TAG...$THIS_TAG" -- ./install-php-extensions)"
+          fi
+          printf 'Release notes:\n%s\n' "$RELEASE_NOTES"
+          printf 'RELEASE_NAME=v%s\n' "$THIS_TAG" >> "$GITHUB_ENV"
+          printf 'RELEASE_NOTES<<EOF\n%s\nEOF\n' "$RELEASE_NOTES" >> "$GITHUB_ENV"
+      - name: Create release
+        if: env.THIS_TAG != ''
+        uses: actions/create-release@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+            tag_name: ${{ env.THIS_TAG }}
+            release_name: ${{ env.RELEASE_NAME }}
+            body: ${{ env.RELEASE_NOTES }}
+            draft: false
+            prerelease: false