Move git operations for UpdateRemoteMirrorService into Gitlab::Git

lib/gitlab/git/remote_mirror.rb

+module Gitlab
+  module Git
+    class RemoteMirror
+      def initialize(repository, ref_name)
+        @repository = repository
+        @ref_name = ref_name
+      end
+
+      def update(only_branches_matching: [], only_tags_matching: [])
+        local_branches = refs_obj(@repository.local_branches, only_refs_matching: only_branches_matching)
+        remote_branches = refs_obj(@repository.remote_branches(@ref_name), only_refs_matching: only_branches_matching)
+
+        updated_branches = changed_refs(local_branches, remote_branches)
+        push_branches(updated_branches.keys) if updated_branches.present?
+
+        delete_refs(local_branches, remote_branches)
+
+        local_tags = refs_obj(@repository.tags, only_refs_matching: only_tags_matching)
+        remote_tags = refs_obj(@repository.remote_tags(@ref_name), only_refs_matching: only_tags_matching)
+
+        updated_tags = changed_refs(local_tags, remote_tags)
+        @repository.push_remote_branches(@ref_name, updated_tags.keys) if updated_tags.present?
+
+        delete_refs(local_tags, remote_tags)
+      end
+
+      private
+
+      def refs_obj(refs, only_refs_matching: [])
+        refs.each_with_object({}) do |ref, refs|
+          next if only_refs_matching.present? && !only_refs_matching.include?(ref.name)
+
+          refs[ref.name] = ref
+        end
+      end
+
+      def changed_refs(local_refs, remote_refs)
+        local_refs.select do |ref_name, ref|
+          remote_ref = remote_refs[ref_name]
+
+          remote_ref.nil? || ref.dereferenced_target != remote_ref.dereferenced_target
+        end
+      end
+
+      def push_branches(branches)
+        default_branch, branches = branches.partition do |branch|
+          @repository.root_ref == branch
+        end
+
+        # Push the default branch first so it works fine when remote mirror is empty.
+        branches.unshift(*default_branch)
+
+        @repository.push_remote_branches(@ref_name, branches)
+      end
+
+      def delete_refs(local_refs, remote_refs)
+        refs = refs_to_delete(local_refs, remote_refs)
+
+        @repository.delete_remote_branches(@ref_name, refs.keys) if refs.present?
+      end
+
+      def refs_to_delete(local_refs, remote_refs)
+        default_branch_id = @repository.commit.id
+
+        remote_refs.select do |remote_ref_name, remote_ref|
+          next false if local_refs[remote_ref_name] # skip if branch or tag exist in local repo
+
+          remote_ref_id = remote_ref.dereferenced_target.try(:id)
+
+          remote_ref_id && @repository.rugged_is_ancestor?(remote_ref_id, default_branch_id)
+        end
+      end
+    end
+  end
+end