Supply author for auto-update commits

Author: rvl

scripts/update-external.nix

@@ -19,7 +19,9 @@ in
     ${script}
 
     git add .
-    git commit --allow-empty -m "Automatic update for $(date)"
+    git commit --allow-empty \
+        --message "Automatic update for $(date)" \
+        --author="IOHK <[email protected]>"
 
     rev=$(git rev-parse HEAD)