Fetch PRs from upstream repo for cherry-picking

Author: bobtista

.github/workflows/build-historical.yml

@@ -112,14 +112,17 @@ jobs:
           git config user.name "GitHub Actions"
           git config user.email "[email protected]"
 
+          UPSTREAM="https://github.com/TheSuperHackers/GeneralsGameCode.git"
+          git remote add upstream "$UPSTREAM" || true
+
           PR_LIST="${{ github.event.inputs.pull_requests }}"
           IFS=',' read -ra PRS <<< "$PR_LIST"
 
           for PR in "${PRS[@]}"; do
             PR=$(echo "$PR" | xargs)
             echo "::group::Applying PR #$PR"
 
-            git fetch origin "pull/$PR/head:pr-$PR"
+            git fetch upstream "pull/$PR/head:pr-$PR"
 
             PR_BASE=$(git merge-base pr-$PR HEAD)
             PR_COMMITS=$(git rev-list --reverse "$PR_BASE..pr-$PR")