For mysterious reasons this unblocks 'git pull'

Closes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/185

Makefile

@@ -109,7 +109,7 @@ gitlab/.git/pull:
 	cd ${gitlab_development_root}/gitlab && \
 		git checkout -- Gemfile.lock db/schema.rb && \
 		git stash && git checkout master && \
-		git pull --ff-only
+		git pull --ff-only upstream master
 gitlab-shell/.git/pull:
 	cd ${gitlab_development_root}/gitlab-shell && \