[Integrated] RFR: Try a bit harder to generate incremental webrevs

[Robin Westberg]

Changeset: 60a4f7f1
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2019-12-05 10:42:50 +0000
URL:       https://git.openjdk.java.net/skara/commit/60a4f7f1

Try a bit harder to generate incremental webrevs

Reviewed-by: ehelin

! bots/mlbridge/src/main/java/org/openjdk/skara/bots/mlbridge/ArchiveItem.java
! bots/mlbridge/src/main/java/org/openjdk/skara/bots/mlbridge/ArchiveMessages.java
! bots/mlbridge/src/main/java/org/openjdk/skara/bots/mlbridge/ArchiveWorkItem.java
! bots/mlbridge/src/test/java/org/openjdk/skara/bots/mlbridge/MailingListBridgeBotTests.java