Don't fetch tags when fetching remote mirror.

* Add the ability to skip tags when fetching a remote repo.
  See: https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/46

app/models/repository.rb

@@ -213,8 +213,8 @@ class Repository
     remote_config["remote.#{name}.prune"] = true
   end
 
-  def fetch_remote(remote)
-    gitlab_shell.fetch_remote(path_with_namespace, remote)
+  def fetch_remote(remote, forced: false, no_tags: false)
+    gitlab_shell.fetch_remote(path_with_namespace, remote, forced: forced, no_tags: no_tags)
   end
 
   def fetch_remote_forced!(remote)

app/services/projects/update_remote_mirror_service.rb

@@ -7,7 +7,7 @@ module Projects
       @errors = []
 
       begin
-        repository.fetch_remote(mirror.ref_name)
+        repository.fetch_remote(mirror.ref_name, no_tags: true)
 
         if divergent_branches.present?
           errors << "The following branches have diverged from their local counterparts: #{divergent_branches.to_sentence}"

lib/gitlab/backend/shell.rb

@@ -50,9 +50,11 @@ module Gitlab
     # Ex.
     #   fetch_remote("gitlab/gitlab-ci", "upstream")
     #
-    def fetch_remote(name, remote, forced: false)
+    def fetch_remote(name, remote, forced: false, no_tags: false)
       args = [gitlab_shell_projects_path, 'fetch-remote', "#{name}.git", remote, '600']
       args << '--force' if forced
+      args << '--no-tags' if no_tags
+
       output, status = Popen::popen(args)
       raise Error, output unless status.zero?
       true