feat: Auto-rebase open PRs when master is updated (#983)

Add workflow to automatically keep open PRs up-to-date:
- Dependabot PRs: uses @dependabot rebase command
- Other non-draft PRs: uses gh pr update-branch --rebase
- Simplify dependabot-auto-merge.yml by removing redundant update step

Author: mPokornyETM

.github/workflows/dependabot-auto-merge.yml

@@ -13,12 +13,6 @@ jobs:
     runs-on: ubuntu-latest
     if: github.actor == 'dependabot[bot]'
     steps:
-      - name: Update branch if behind
-        run: gh pr update-branch --rebase "$PR_URL" || true
-        env:
-          PR_URL: ${{ github.event.pull_request.html_url }}
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Enable auto-merge
         run: gh pr merge --auto --squash "$PR_URL"
         env:

.github/workflows/rebase-open-prs.yml

@@ -0,0 +1,31 @@
+# Rebase all open PRs when master is updated
+# This keeps PRs up-to-date automatically
+name: Rebase Open PRs
+
+on:
+  push:
+    branches:
+      - master
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  rebase-open-prs:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Rebase all open PRs
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GH_REPO: ${{ github.repository }}
+        run: |
+          gh pr list --state open --json number,author,isDraft --jq '.[] | select(.isDraft == false) | "\(.number) \(.author.login)"' | while read pr author; do
+            if [ "$author" = "dependabot[bot]" ]; then
+              echo "Requesting rebase for Dependabot PR #$pr"
+              gh pr comment "$pr" --body "@dependabot rebase"
+            else
+              echo "Updating branch for PR #$pr"
+              gh pr update-branch --rebase "$pr" || true
+            fi
+          done