Fix sync-dependencies infinite PR loop

The previous workflow tried fast-forward master into dependencies
and fell back to a deps-sync branch + PR on failure. Under squash
merges (used for both dependencies -> master and deps-sync ->
dependencies), the branches diverge permanently after the first
sync, so FF never succeeds and every push to master creates a
fresh deps-sync PR.

Open the PR with head=master directly and gate creation on a tree
diff against dependencies. When trees already match (typical after
a dependencies -> master merge) no PR is opened. This breaks the
loop and drops the deps-sync branch from the design.

Author: nerjs

.github/workflows/ci-deps.yml

@@ -3,9 +3,7 @@ name: CI (deps)
 on:
   workflow_dispatch:
   push:
-    branches:
-      - dependencies
-      - deps-sync
+    branches: [dependencies]
   pull_request:
     branches: [dependencies]
 

.github/workflows/sync-dependencies.yml

@@ -22,43 +22,26 @@ jobs:
           fetch-depth: 0
           token: ${{ secrets.RELEASE_TOKEN }}
 
-      - name: Configure git
-        run: |
-          git config user.name "nerjs"
-          git config user.email "nerjs.stap@gmail.com"
-
-      - name: Sync or prepare deps-sync
-        id: sync
+      - name: Ensure dependencies branch and open PR if drift
+        env:
+          GH_TOKEN: ${{ secrets.RELEASE_TOKEN }}
         run: |
           set -euo pipefail
           if ! git ls-remote --heads origin dependencies | grep -q dependencies; then
             git push origin master:dependencies
-            echo "result=created" >> "$GITHUB_OUTPUT"
             exit 0
           fi
-          git fetch origin dependencies:dependencies
-          git checkout dependencies
-          if git merge --ff-only origin/master; then
-            git push origin dependencies
-            echo "result=ff" >> "$GITHUB_OUTPUT"
+          git fetch origin dependencies
+          if git diff --quiet origin/master origin/dependencies; then
+            echo "master and dependencies trees match; nothing to sync"
             exit 0
           fi
-          git checkout -B deps-sync origin/master
-          git push --force-with-lease origin deps-sync
-          echo "result=needs-pr" >> "$GITHUB_OUTPUT"
-
-      - name: Ensure PR deps-sync -> dependencies
-        if: steps.sync.outputs.result == 'needs-pr'
-        env:
-          GH_TOKEN: ${{ secrets.RELEASE_TOKEN }}
-        run: |
-          set -euo pipefail
-          existing=$(gh pr list --base dependencies --head deps-sync --state open --json number --jq '.[0].number // empty')
+          existing=$(gh pr list --base dependencies --head master --state open --json number --jq '.[0].number // empty')
           if [ -z "$existing" ]; then
             gh pr create \
-              --base dependencies --head deps-sync \
+              --base dependencies --head master \
               --title "Sync master into dependencies" \
-              --body "Auto-generated by sync-dependencies.yml. Resolve conflicts on deps-sync, then merge into dependencies."
+              --body "Auto-generated by sync-dependencies.yml. Merge to bring master changes into dependencies."
           else
             echo "PR #$existing already open"
           fi