avoid debian folder to be wiped out by pushed changes

.gitlab-ci.yml

@@ -13,7 +13,7 @@ deb:
   stage: build
   allow_failure: false
   script:
-    - git checkout incoming && gbp buildpackage --git-ignore-new --git-force-create --git-upstream-tree=SLOPPY --git-no-pristine-tar --git-debian-branch=debian --git-builder='debuild -us -uc'
+    - mv debian debian.bk && git checkout incoming && mv debian.bk debian && gbp buildpackage --git-ignore-new --git-force-create --git-upstream-tree=SLOPPY --git-no-pristine-tar --git-debian-branch=debian --git-builder='debuild -us -uc'
     - mv ../*.deb .
   tags:
     - linux