Allow user to skip archive creation on backup

Don't create a (tar) archive if the user specified SKIP=tar when
creating a backup.

Allow restore from untarred backups (they don't have easily accesible
timestamps, so just give such a backup priority if it's present).

Document the festure.

Addresses https://gitlab.com/gitlab-org/gitlab/issues/15179

doc/raketasks/backup_restore.md

@@ -683,7 +683,7 @@ lose access to your GitLab server.
 
 You may also want to restore any TLS keys, certificates, or [SSH host keys](https://superuser.com/questions/532040/copy-ssh-keys-from-one-server-to-another-server/532079#532079).
 
-Starting with GitLab12.9 if an untarred backup (like the ones made with
+Starting with GitLab 12.9 if an untarred backup (like the ones made with
 `SKIP=tar`) is found, and no backup is chosen with `BACKUP=<timestamp>`, the
 untarred backup is used.
 

lib/backup/manager.rb

@@ -126,6 +126,7 @@ module Backup
     end
 
     def unpack
+      cleanup_required = true
       Dir.chdir(backup_path) do
         if ENV['BACKUP'].present?
           # User has indicated which backup to restore
@@ -164,6 +165,7 @@ module Backup
             exit 1
           end
         end
+      end
       true
     end
 

lib/tasks/gitlab/backup.rake

@@ -41,7 +41,7 @@ namespace :gitlab do
 
       backup = Backup::Manager.new(progress)
       cleanup_required = backup.unpack
-      backup.verify_restore
+      backup.verify_backup_version
 
       unless backup.skipped?('db')
         begin