[Integrated] RFR: Proper selection of merge commit to squash commits onto for merge style PRs

[Robin Westberg]

Changeset: c0a0a508
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2020-03-30 15:00:31 +0000
URL:       https://git.openjdk.java.net/skara/commit/c0a0a508

Proper selection of merge commit to squash commits onto for merge style PRs

Reviewed-by: ehelin

! bots/pr/src/main/java/org/openjdk/skara/bots/pr/CheckRun.java
! bots/pr/src/main/java/org/openjdk/skara/bots/pr/PullRequestInstance.java
! bots/pr/src/test/java/org/openjdk/skara/bots/pr/MergeTests.java