When pushing an amended commit with the %edit option, the ReplaceRequest
has null info, which causes NPE when trying to use it to get the subject
of the new patch set. This results in the message:
"internal error while processing changes"
to be shown to the user instead of the "Updated Changes" list.
Use the ReplaceRequest's newCommit instead.
Also update AbstractPushForReview#testPushForMasterAsEdit to confirm that
the expected "Updated Changes" output is present.
Bug: Issue 4236
Change-Id: I82983219a3220d21f043fdc662f561e291fc0746
a0157917f2