[Integrated] RFR: 362: Only amend merge commits that has the target branch as parent

[Robin Westberg]

Changeset: fed35009
Author:    Robin Westberg <rwestberg at openjdk.org>
Date:      2020-04-16 12:31:00 +0000
URL:       https://git.openjdk.java.net/skara/commit/fed35009

362: Only amend merge commits that has the target branch as parent

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
! vcs/src/main/java/org/openjdk/skara/vcs/git/GitRepository.java