Properly fix wiki restore.

ProjectWiki.new() creates a new wiki git repository, so any tries
to bare clone a bundle fail. With this patch we remove the newly
created wiki.git before restoring from the backup bundle.

lib/backup/repository.rb

@@ -59,7 +59,7 @@ module Backup
       FileUtils.mkdir_p(repos_path)
 
       Project.find_each(batch_size: 1000) do |project|
-        $progress.print "#{project.path_with_namespace} ... "
+        $progress.print " * #{project.path_with_namespace} ... "
 
         project.namespace.ensure_dir_exist if project.namespace
 
@@ -79,13 +79,14 @@ module Backup
 
         wiki = ProjectWiki.new(project)
 
+        if File.exists?(path_to_bundle(wiki))
           $progress.print " * #{wiki.path_with_namespace} ... "
 
-        if File.exists?(path_to_bundle(wiki))
+          # If a wiki bundle exists, first remove the empty repo
+          # that was initialized with ProjectWiki.new() and then
+          # try to restore with 'git clone --bare'.
+          FileUtils.rm_rf(path_to_repo(wiki))
           cmd = %W(git clone --bare #{path_to_bundle(wiki)} #{path_to_repo(wiki)})
-        else
-          cmd = %W(git init --bare #{path_to_repo(wiki)})
-        end
 
           if system(*cmd, silent)
             $progress.puts " [DONE]".green
@@ -95,6 +96,7 @@ module Backup
             abort 'Restore failed'
           end
         end
+      end
 
       $progress.print 'Put GitLab hooks in repositories dirs'.yellow
       cmd = "#{Gitlab.config.gitlab_shell.path}/bin/create-hooks"