drone: fix cron jobs for user branches

.drone.yml

@@ -4,6 +4,25 @@ type: docker
 name: Upstreaming
 
 steps:
+  - name: "Setup git repos and SSH access"
+    image: alpine/git
+    when:
+      event:
+        - cron
+      cron:
+        - sync-main-with-upstream
+        - sync-b12f-with-main
+        - sync-teutat3s-with-main
+    environment:
+      GITEA_SSH_KEY:
+        from_secret: gitea_ssh_key
+    commands:
+      - ./.drone/setup_ssh.sh
+      - git fetch
+      - git remote add devos git@git.b12f.io:pub-solar/devos
+      - git remote set-url origin git@git.b12f.io:pub-solar/os
+      - git fetch --all
+
   - name: "Sync 'devos' branch with upstream"
     image: alpine/git
     when:
@@ -16,11 +35,7 @@ steps:
         from_secret: gitea_ssh_key
     commands:
       - ./.drone/setup_ssh.sh
-      - git fetch
-      - git checkout devos
-      - git remote add devos git@git.b12f.io:pub-solar/devos
-      - git remote set-url origin git@git.b12f.io:pub-solar/os
-      - git fetch --all
+      - git checkout origin/devos
       - git merge -X theirs devos/main
       - git push origin devos