added version check on import

lib/gitlab/import_export/import_service.rb

@@ -16,7 +16,7 @@ module Gitlab
       def execute
         Gitlab::ImportExport::Importer.import(archive_file: @archive_file,
                                               shared: @shared)
-        if [restore_project_tree, restore_repo, restore_wiki_repo].all?
+        if [restore_version, restore_project_tree, restore_repo, restore_wiki_repo].all?
           project_tree.project
         else
           project_tree.project.destroy if project_tree.project
@@ -26,6 +26,10 @@ module Gitlab
 
       private
 
+      def restore_version
+        Gitlab::ImportExport::VersionRestorer.restore(shared: @shared)
+      end
+
       def restore_project_tree
         project_tree.restore
       end

lib/gitlab/import_export/version_restorer.rb

+module Gitlab
+  module ImportExport
+    class VersionRestorer
+
+      def self.restore(*args)
+        new(*args).restore
+      end
+
+      def initialize(shared:)
+        @shared = shared
+      end
+
+      def restore
+        version = File.open(version_file, &:readline)
+        verify_version!(version)
+      rescue => e
+        @shared.error(e)
+        false
+      end
+
+      private
+
+      def version_file
+        File.join(@shared.export_path, Gitlab::ImportExport.version_filename)
+      end
+
+      def verify_version!(version)
+        if Gem::Version.new(version) > Gem::Version.new(Gitlab::ImportExport.VERSION)
+          raise Gitlab::ImportExport::Error("Import version mismatch: Required <= #{Gitlab::ImportExport.VERSION} but was #{version}")
+        else
+          true
+        end
+      end
+    end
+  end
+end

lib/gitlab/import_export/version_saver.rb

@@ -15,7 +15,7 @@ module Gitlab
           file.write(Gitlab::ImportExport.VERSION)
         end
       rescue => e
-        @shared.error(e.message)
+        @shared.error(e)
         false
       end