Correctly restore empty repositories.

If a project is being restored, but there is no bundle file, the project was
empty when it was backed up.  In this case, just use git init --base to create a
new bare repository.

lib/backup/repository.rb

@@ -59,7 +59,13 @@ module Backup
 
         project.namespace.ensure_dir_exist if project.namespace
 
-        if system(*%W(git clone --bare #{path_to_bundle(project)} #{path_to_repo(project)}), silent)
+        if File.exists?(path_to_bundle(project))
+          cmd = %W(git clone --bare #{path_to_bundle(project)} #{path_to_repo(project)})
+        else
+          cmd = %W(git init --bare #{path_to_repo(project)})
+        end
+
+        if system(*cmd, silent)
           puts "[DONE]".green
         else
           puts "[FAILED]".red