Merge branch 'sh-bump-gitaly-version-1.12.0' into 'master'

Bump Gitaly version to v1.12.0

See merge request gitlab-org/gitlab-ce!23996

GITALY_SERVER_VERSION

-1.9.0
+1.12.0

lib/api/helpers.rb

@@ -163,10 +163,12 @@ module API
     end
 
     def find_branch!(branch_name)
+      if Gitlab::GitRefValidator.validate(branch_name)
         user_project.repository.find_branch(branch_name) || not_found!('Branch')
-    rescue Gitlab::Git::CommandError
+      else
         render_api_error!('The branch refname is invalid', 400)
       end
+    end
 
     def find_project_label(id)
       labels = available_labels_for(user_project)