fix TODO check

Author: CritasWang

.github/workflows/todos-check.yml

@@ -25,14 +25,11 @@ jobs:
           # Fetch the target branch
           git fetch origin $GITHUB_BASE_REF
           
-          # Check if there is a common ancestor
-          if git merge-base --is-ancestor origin/$GITHUB_BASE_REF HEAD; then
-            # Get the diff of the changes
-            DIFF=$(git diff origin/$GITHUB_BASE_REF...HEAD)
-          else
-            # If no common ancestor, compare with the initial commit
-            DIFF=$(git diff $(git hash-object -t tree /dev/null) HEAD)
-          fi
+          git switch -c check_branch
+          
+          # Get the diff of the changes
+          DIFF=$(git diff origin/$GITHUB_BASE_REF check_branch)
+          
   
           # Check the diff for TODOs
           if echo "$DIFF" | grep -Eq '^\+.*(TODO|FIXME)'; then