Test if remote repository exists before cloning

When a repository does not exist on a remote, Gitaly won't be able to
clone it. This is correct behaviour, but from the clients perspective a
change in behaviour.

This change implements the client side changes that allows Gitaly to
execute a `git ls-remote <remote-url> HEAD`. This way the client has no
need to shell out to Git.

In the situation where multiple Gitalies are available, one is chosen at
random.

This commit closes https://gitlab.com/gitlab-org/gitlab-ce/issues/43929,
while its also a part of https://gitlab.com/gitlab-org/gitaly/issues/1084

GITALY_SERVER_VERSION

-0.91.0
+0.92.0

Gemfile

@@ -420,7 +420,7 @@ group :ed25519 do
 end
 # Gitaly GRPC client
-gem 'gitaly-proto', '~> 0.88.0', require: 'gitaly'
+gem 'gitaly-proto', '~> 0.91.0', require: 'gitaly'
 gem 'grpc', '~> 1.10.0'
 # Locked until https://github.com/google/protobuf/issues/4210 is closed

Gemfile.lock

@@ -289,7 +289,7 @@ GEM
       po_to_json (>= 1.0.0)
       rails (>= 3.2.0)
     gherkin-ruby (0.3.2)
-    gitaly-proto (0.88.0)
+    gitaly-proto (0.91.0)
       google-protobuf (~> 3.1)
       grpc (~> 1.0)
     github-linguist (5.3.3)
@@ -1058,7 +1058,7 @@ DEPENDENCIES
   gettext (~> 3.2.2)
   gettext_i18n_rails (~> 1.8.0)
   gettext_i18n_rails_js (~> 1.3)
-  gitaly-proto (~> 0.88.0)
+  gitaly-proto (~> 0.91.0)
   github-linguist (~> 5.3.3)
   gitlab-flowdock-git-hook (~> 1.0.1)
   gitlab-markup (~> 1.6.2)

changelogs/unreleased/zj-remote-repo-exists.yml

+---
+title: Test if remote repository exists when importing wikis
+merge_request:
+author:
+type: fixed

lib/gitlab/gitaly_client.rb

@@ -83,6 +83,10 @@ module Gitlab
       end
     end
+    def self.random_storage
+      Gitlab.config.repositories.storages.keys.sample
+    end
+
     def self.address(storage)
       params = Gitlab.config.repositories.storages[storage]
       raise "storage not found: #{storage.inspect}" if params.nil?

lib/gitlab/gitaly_client/remote_service.rb

@@ -3,6 +3,17 @@ module Gitlab
     class RemoteService
       MAX_MSG_SIZE = 128.kilobytes.freeze
+      def self.exists?(remote_url)
+        request = Gitaly::FindRemoteRepositoryRequest.new(remote: remote_url)
+
+        response = GitalyClient.call(GitalyClient.random_storage,
+                                     :remote_service,
+                                     :find_remote_repository, request,
+                                     timeout: GitalyClient.medium_timeout)
+
+        response.exists
+      end
+
       def initialize(repository)
         @repository = repository
         @gitaly_repo = repository.gitaly_repository

lib/gitlab/github_import/importer/repository_importer.rb

@@ -16,7 +16,8 @@ module Gitlab
         # Returns true if we should import the wiki for the project.
         def import_wiki?
           client.repository(project.import_source)&.has_wiki &&
-            !project.wiki_repository_exists?
+            !project.wiki_repository_exists? &&
+            Gitlab::GitalyClient::RemoteService.exists?(wiki_url)
         end
         # Imports the repository data.
@@ -55,7 +56,6 @@ module Gitlab
         def import_wiki_repository
           wiki_path = "#{project.disk_path}.wiki"
-          wiki_url = project.import_url.sub(/\.git\z/, '.wiki.git')
           storage_path = project.repository_storage_path
           gitlab_shell.import_repository(storage_path, wiki_path, wiki_url)
@@ -70,6 +70,10 @@ module Gitlab
           end
         end
+        def wiki_url
+          project.import_url.sub(/\.git\z/, '.wiki.git')
+        end
+
         def update_clone_time
           project.update_column(:last_repository_updated_at, Time.zone.now)
         end

spec/lib/gitlab/gitaly_client/remote_service_spec.rb

@@ -58,4 +58,14 @@ describe Gitlab::GitalyClient::RemoteService do
       client.update_remote_mirror(ref_name, only_branches_matching)
     end
   end
+
+  describe '.exists?' do
+    context "when the remote doesn't exist" do
+      let(:url) { 'https://gitlab.com/gitlab-org/ik-besta-niet-of-ik-word-geplaagd.git' }
+
+      it 'returns false' do
+        expect(described_class.exists?(url)).to be(false)
+      end
+    end
+  end
 end

spec/lib/gitlab/github_import/importer/repository_importer_spec.rb

@@ -38,8 +38,12 @@ describe Gitlab::GithubImport::Importer::RepositoryImporter do
       expect(project)
         .to receive(:wiki_repository_exists?)
         .and_return(false)
-      expect(importer.import_wiki?).to eq(true)
+      expect(Gitlab::GitalyClient::RemoteService)
+        .to receive(:exists?)
+        .with("foo.wiki.git")
+        .and_return(true)
+      expect(importer.import_wiki?).to be(true)
     end
     it 'returns false if the GitHub wiki is disabled' do