Fix release workflow

gh(1) needs a git repository to work with, so checkout the code before
using it.
While here, adjust the workflow/action name.

Author: smortex

.github/workflows/release.yaml

@@ -1,5 +1,5 @@
 ---
-name: Gem Release
+name: Release
 
 on:
   push:
@@ -8,7 +8,7 @@ on:
 
 jobs:
   release:
-    name: Release gem
+    name: Release
     runs-on: ubuntu-24.04
     # Optional but recommended to use a specific environment
     environment: release
@@ -19,6 +19,10 @@ jobs:
       contents: write
 
     steps:
+      - name: Checkout current PR
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - name: Create Release Page
         shell: bash
         env: