RFR: 1466: Empty backport causes endless retries of command

[Magnus Ihse Bursie]

On Fri, 3 Jun 2022 23:21:59 GMT, Erik Joelsson <erikj at openjdk.org> wrote:

> If a user tries to /backport a commit that results in an empty change, the BackportCommand fails to realize this and just errors out. It will then endlessly retry the command. This patch makes the BackportCommand detect an empty change and report it to the user.

LGTM

-------------

Marked as reviewed by ihse (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/1329