Allow asynchronous rebase operations to be monitored

This MR introduces tracking of the `rebase_jid` for merge requests. As
with `merge_ongoing?`, `rebase_in_progress?` will now return true if a
rebase is proceeding in sidekiq.

After one release, we should remove the Gitaly-based lookup of rebases.
It is much better to track this kind of thing via the database.

1 files changed, 9 insertions, 0 deletions

diff --git a/db/migrate/20190621151636_add_merge_request_rebase_jid.rb b/db/migrate/20190621151636_add_merge_request_rebase_jid.rb
new file mode 100644
index 00000000000..1fed5690ead
--- /dev/null
+++ b/db/migrate/20190621151636_add_merge_request_rebase_jid.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class AddMergeRequestRebaseJid < ActiveRecord::Migration[5.1]
+  DOWNTIME = false
+
+  def change
+    add_column :merge_requests, :rebase_jid, :string
+  end
+end