Breaking change in 1.0.12 because of new releaseNextCommitMessage param

[JMLamodiere]

As explained in #256 , many projects running with a CI have tweeked the parameter releaseCommitMessage to add [ci skip] :

releaseCommitMessage := s"[ci skip] Setting version to ${(version in ThisBuild).value}"

Otherwise the CI triggers an infinite loop after a merge on master :

• the CI hooks trigger sbt-release
• sbt-release add a commit message
• the commit message triggers the CI

But after upgrading to 1.0.12, which should have no breaking change according to semantic versionning, this infinite loop will re-appear. It is mandatory to also configure the new parameter releaseNextCommitMessage added by e1abd0a#diff-f3ca64c8ba9a5c72fa812cb7fbbc27a4R238 to add [ci-skip] .

I fear many projects will face this breaking change. In our case, we upgraded many sbt plugin and maven dependencies at once, we didn't know about this [ci-skip] tricks (added by previous developers in our project), so we didn't figure out right away that the sbt-release upgrade was in cause.

I suggest that the default value of releaseNextCommitMessage should be the value configured for releaseCommitMessage. This way, it keeps the behaviour of version 1.0.11 and fix the breaking change.