workflow: use rebase instead of merge

.gitea/workflows/update-flake.yaml

@@ -30,14 +30,13 @@ jobs:
             git log --oneline -5
             echo "----------"
             git log --oneline -5 origin/main
+            echo .
 
             if [ $commits_ahead -ne 0 ]
             then
-              git fetch origin
-              git merge -X theirs --squash origin/main
-              git commit -m "Merge main branch squashed $(date -I)"
+              git rebase -X theirs origin/main
             else
-              echo "Merge not necessary"
+              echo "Rebase not necessary"
             fi
 
       - name: Set up Nix
@@ -54,4 +53,4 @@ jobs:
           git diff --cached --quiet && echo "No changes to commit." && exit 0
 
           git commit -m "Update flake.lock $(date -I)"
-          git push origin flake-updates
+          git push --force-with-lease origin flake-updates