Add keep_divergent_refs to Git::RemoteMirror

This receives the flag from `RemoteMirror#update_repository` and passes
the flag to the Gitaly client.

lib/gitlab/git/remote_mirror.rb

@@ -5,14 +5,15 @@ module Gitlab
     class RemoteMirror
       include Gitlab::Git::WrapsGitalyErrors
 
-      attr_reader :repository, :ref_name, :only_branches_matching, :ssh_key, :known_hosts
+      attr_reader :repository, :ref_name, :only_branches_matching, :ssh_key, :known_hosts, :keep_divergent_refs
 
-      def initialize(repository, ref_name, only_branches_matching: [], ssh_key: nil, known_hosts: nil)
+      def initialize(repository, ref_name, only_branches_matching: [], ssh_key: nil, known_hosts: nil, keep_divergent_refs: false)
         @repository = repository
         @ref_name = ref_name
         @only_branches_matching = only_branches_matching
         @ssh_key = ssh_key
         @known_hosts = known_hosts
+        @keep_divergent_refs = keep_divergent_refs
       end
 
       def update
@@ -21,7 +22,8 @@ module Gitlab
             ref_name,
             only_branches_matching,
             ssh_key: ssh_key,
-            known_hosts: known_hosts
+            known_hosts: known_hosts,
+            keep_divergent_refs: keep_divergent_refs
           )
         end
       end

spec/lib/gitlab/git/remote_mirror_spec.rb

@@ -7,14 +7,14 @@ describe Gitlab::Git::RemoteMirror do
     let(:project) { create(:project, :repository) }
     let(:repository) { project.repository }
     let(:ref_name) { 'foo' }
-    let(:options) { { only_branches_matching: ['master'], ssh_key: 'KEY', known_hosts: 'KNOWN HOSTS' } }
+    let(:options) { { only_branches_matching: ['master'], ssh_key: 'KEY', known_hosts: 'KNOWN HOSTS', keep_divergent_refs: true } }
 
     subject(:remote_mirror) { described_class.new(repository, ref_name, **options) }
 
     it 'delegates to the Gitaly client' do
       expect(repository.gitaly_remote_client)
         .to receive(:update_remote_mirror)
-        .with(ref_name, ['master'], ssh_key: 'KEY', known_hosts: 'KNOWN HOSTS')
+        .with(ref_name, ['master'], ssh_key: 'KEY', known_hosts: 'KNOWN HOSTS', keep_divergent_refs: true)
 
       remote_mirror.update
     end