Fix GitHub Import for open PRs from a fork

lib/gitlab/github_import/importer.rb

@@ -148,7 +148,7 @@ module Gitlab
             rescue => e
               errors << { type: :pull_request, url: Gitlab::UrlSanitizer.sanitize(gh_pull_request.url), errors: e.message }
             ensure
-              clean_up_restored_branches(gh_pull_request)
+              clean_up_restored_branches(gh_pull_request) unless gh_pull_request.opened?
             end
           end
         end

lib/gitlab/github_import/pull_request_formatter.rb

@@ -60,6 +60,18 @@ module Gitlab
         source_branch.repo.id != target_branch.repo.id
       end
 
+      def opened?
+        state == 'opened'
+      end
+
+      def closed?
+        state == 'closed'
+      end
+
+      def merged?
+        state == 'merged'
+      end
+
       private
 
       def state

spec/lib/gitlab/github_import/pull_request_formatter_spec.rb

@@ -306,4 +306,28 @@ describe Gitlab::GithubImport::PullRequestFormatter, lib: true do
       expect(pull_request.url).to eq 'https://api.github.com/repos/octocat/Hello-World/pulls/1347'
     end
   end
+
+  describe '#opened?' do
+    let(:raw_data) { double(base_data.merge(state: 'open')) }
+
+    it 'returns true when state is "open"' do
+      expect(pull_request.opened?).to be_truthy
+    end
+  end
+
+  describe '#closed?' do
+    let(:raw_data) { double(base_data.merge(state: 'closed')) }
+
+    it 'returns true when state is "closed"' do
+      expect(pull_request.closed?).to be_truthy
+    end
+  end
+
+  describe '#merged?' do
+    let(:raw_data) { double(base_data.merge(state: 'closed', merged_at: Date.today)) }
+
+    it 'returns true when state is "closed" and merged_at is set' do
+      expect(pull_request.merged?).to be_truthy
+    end
+  end
 end