simplify token gen

Author: roiser

.github/workflows/mg5_codegen.yml

@@ -46,44 +46,13 @@ jobs:
             echo "❌ clang-format check failed."
           fi
 
-      - name: Decode private key
-        run: |
-          echo "${{ secrets.GH_APP_PRIVATE_KEY }}" | base64 --decode > app.pem
-          chmod 600 app.pem
-      
-      - name: Generate installation token
+      - name: Generate GitHub App token
         id: app-token
-        uses: actions/github-script@v7
+        uses: actions/create-github-app-token@v1
         with:
-          script: |
-            const fs = require("fs");
-            const jwt = require("jsonwebtoken");
-
-            const privateKey = fs.readFileSync("app.pem", "utf8");
-
-            const now = Math.floor(Date.now() / 1000);
-            const payload = {
-              iat: now - 60,
-              exp: now + 600,
-              iss: process.env.APP_ID
-            };
-
-            const token = jwt.sign(payload, privateKey, { algorithm: "RS256" });
-
-            const response = await github.request(
-              "POST /app/installations/{installation_id}/access_tokens",
-              {
-                installation_id: process.env.APP_INSTALLATION_ID,
-                headers: {
-                  authorization: `Bearer ${token}`
-                }
-              }
-            );
-
-            return response.data.token;
-        env:
-          APP_ID: ${{ secrets.GH_APP_ID }}
-          APP_INSTALLATION_ID: ${{ secrets.GH_APP_INSTALLATION_ID }}
+          app-id: ${{ secrets.GH_APP_ID }}
+          private-key: ${{ secrets.GH_APP_PRIVATE_KEY }}
+          installation-id: ${{ secrets.GH_APP_INSTALLATION_ID }}
 
       - name: Commit to target repository
         if: ${{ steps.clang-format-check.outputs.files2format == '8' }}
@@ -96,7 +65,7 @@ jobs:
           git config --global user.email "github-actions@users.noreply.github.com"
           
           # Clone target repo
-          git clone https://x-access-token:${{ steps.app-token.outputs.result }}@github.com/${TARGET_REPO}.git
+          git clone https://x-access-token:${{ steps.app-token.outputs.token }}@github.com/${TARGET_REPO}.git
           cd madgraph4gpu-generated-processes
           
           # Create branch based on PR number