chore: add workflow to generate changelog on v*-tags push

.github/workflows/changelog.yml

@@ -1,33 +1,33 @@
-name: Generate changelog
-
-on: workflow_dispatch
+on:
+  push:
+    tags:
+      - 'v*'
 
 jobs:
-  generate-changelog:
+  changelog:
     name: Generate changelog
-    runs-on: ubuntu-20.04
-    outputs:
-      release_body: ${{ steps.release.outputs.release_body }}
+    runs-on: ubuntu-latest
     steps:
       - name: Checkout
         uses: actions/checkout@v2
         with:
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          ref: ${{ github.event.pull_request.head.ref }}
           fetch-depth: 0
+
       - name: Generate a changelog
         uses: orhun/git-cliff-action@v1
         id: git-cliff
         with:
           config: cliff.toml
-          args: --output CHANGELOG.md
+          args: --verbose
         env:
           OUTPUT: CHANGELOG.md
-      - name: Set the release body
-        id: release
-        shell: bash
-        run: |
-          r=$(cat ${{ steps.git-cliff.outputs.changelog }})
-          r="$(printf "$r" | tail -n +3)"
-          r="${r//'%'/'%25'}"
-          r="${r//$'\n'/'%0A'}"
-          r="${r//$'\r'/'%0D'}"
-          echo "::set-output name=release_body::$r"
+
+      - name: Commit the changelog
+        uses: EndBug/add-and-commit@v9
+        with:
+          add: 'CHANGELOG.md'
+          author_name: Git Cliff
+          committer_name: Git Cliff
+          message: 'chore: update CHANGELOG.md'