Automate upgrade commits

Summary:
Openfire releases are frequent, and timely notifications are sent
to administrators through XMPP.

This script helps to prepare the change for review.

Test Plan:
Tested to prepare 4.5.1 upgrade at df6c523e005c.

Linted with Shellcheck.

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D2171