Fix backup restoration whith pre-existing wiki

changelogs/unreleased/118783-restoring-wikis-fails.yml

+---
+title: Fix backup restoration with pre-existing wiki
+merge_request: 24394
+author:
+type: fixed

lib/backup/repository.rb

@@ -96,6 +96,7 @@ module Backup
         end
 
         wiki = ProjectWiki.new(project)
+        wiki.repository.remove rescue nil
         path_to_wiki_bundle = path_to_bundle(wiki)
 
         if File.exist?(path_to_wiki_bundle)

spec/lib/backup/repository_spec.rb

@@ -86,6 +86,22 @@ describe Backup::Repository do
         expect(pool_repository.object_pool.exists?).to be(true)
       end
     end
+
+    it 'cleans existing repositories' do
+      wiki_repository_spy = spy(:wiki)
+
+      allow_next_instance_of(ProjectWiki) do |project_wiki|
+        allow(project_wiki).to receive(:repository).and_return(wiki_repository_spy)
+      end
+
+      expect_next_instance_of(Repository) do |repo|
+        expect(repo).to receive(:remove)
+      end
+
+      subject.restore
+
+      expect(wiki_repository_spy).to have_received(:remove)
+    end
   end
 
   describe '#empty_repo?' do