fix: rebase on latest master before pushing star history chart (#11240)

* fix: rebase on latest master before pushing star history chart

The daily star history workflow git push was rejected with a
non-fast-forward error because new commits landed on master between
the checkout and the push. Fetch full history (fetch-depth: 0) and
rebase the generated commit on top of the latest remote branch before
pushing so the workflow no longer fails when master has moved.

* fix: retry rebase-and-push to handle concurrent master updates

Address review feedback: a one-shot rebase still races if master advances
between the rebase and the push. Match the bounded retry loop used by
java_release.yml — push first, and on rejection rebase and retry up to
five times before failing.

* fix: serialize runs and ensure every rebase is followed by a push

Address review feedback:
- Devin (line 54-55): the old loop rebased after the 5th failed push but
  never pushed the rebased commit. Restructure so each rebase (attempts
  2-5) is followed by a push attempt, with a clear 5-attempt cap.
- Greptile: overlapping runs could conflict on the SVG during rebase.
  Add a concurrency group (cancel-in-progress: true, matching the repo
  convention) so only one chart regeneration runs at a time.

* fix: scope concurrency by ref and guard rebase against transient failures

Address review feedback:
- Devin (line 16): the global star-history concurrency group let a manual
  run on another branch cancel an in-flight daily master update. Scope
  the group by github.ref so only same-branch runs cancel each other.
- Greptile (line 58): git pull --rebase runs under the fail-fast shell,
  so a transient fetch error or conflict aborted the whole step before
  remaining attempts ran. Guard the rebase so a failure aborts the
  in-progress rebase and continues to the next attempt instead.

.github/workflows/star_history.yml

@@ -9,6 +9,14 @@ on:
 permissions:
   contents: write
 
+concurrency:
+  # Only one chart regeneration per branch at a time; a newer run on the same
+  # branch cancels an in-flight one so overlapping runs never conflict on
+  # note/star_history.svg during rebase. Scoped by ref so a manual run on
+  # another branch can't cancel the daily master update.
+  group: star-history-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   render:
     name: Regenerate star history chart
@@ -17,6 +25,9 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v7
+        with:
+          # Full history so the chart commit can rebase onto a moved master.
+          fetch-depth: 0
 
       - name: Set up Python
         uses: actions/setup-python@v7
@@ -43,4 +54,21 @@ jobs:
           fi
           git add note/star_history.svg
           git commit -m "docs: regenerate star history chart"
-          git push
+          # Rebase and retry so a concurrent push to master doesn't lose the chart.
+          for attempt in 1 2 3 4 5; do
+            if [ "$attempt" -gt 1 ]; then
+              # Guard the rebase: a transient fetch error or conflict must not
+              # abort the fail-fast shell before the remaining attempts run.
+              if ! git pull --rebase origin "$GITHUB_REF_NAME"; then
+                echo "rebase failed (attempt ${attempt}); aborting and retrying"
+                git rebase --abort || true
+                continue
+              fi
+            fi
+            if git push origin HEAD:"$GITHUB_REF_NAME"; then
+              exit 0
+            fi
+            echo "push rejected (attempt ${attempt}); will rebase and retry"
+          done
+          echo "::error::could not push star history chart after retries"
+          exit 1