ci: tighten last_modified workflow

Author: lyzhang0113

.github/workflows/update-last-modified.yml

@@ -1,4 +1,4 @@
-name: Update last_modified
+name: Update last_modified
 
 on:
   pull_request:
@@ -11,8 +11,13 @@ on:
     paths:
       - "_articles/faq/*.md"
 
+concurrency:
+  group: update-last-modified-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
 permissions:
   contents: write
+  pull-requests: read
 
 jobs:
   update-on-master-pr:
@@ -45,7 +50,7 @@ jobs:
         shell: bash
         run: |
           set -euo pipefail
-          timestamp="$(date '+%Y-%m-%d %H:%M:%S %z')"
+          timestamp="$(TZ=UTC date '+%Y-%m-%d %H:%M:%S +0000')"
 
           while IFS= read -r file; do
             [[ -f "$file" ]] || continue
@@ -87,4 +92,5 @@ jobs:
             git add "$file"
           done < changed_files.txt
           git commit -m "chore: update last_modified timestamps"
+          git pull --rebase origin "${{ github.event.pull_request.head.ref }}"
           git push origin HEAD:${{ github.event.pull_request.head.ref }}