I was looking back at a change I reviewed and realized that a subsequent patch set (commit fae8daa658c1) does not correctly report durations of 1 hour or more. For example, if the upgrade takes 4567 seconds (1 hour 16 minutes 7 seconds), the "Done in [...]" message would include:
var_dump((new MWTimestamp)->diff(new MWTimestamp(time()-4567))->format('%i:%S'));
string(5) "16:07"
Version: 1.24rc
Severity: trivial