When the plugin checks out the branches and tries to merge the feature branch to the integration branch, it always outputs "Merge failure" without further information. It happens all the time even with no relevant changes compared to the integration branch. This does not happen when using version 2.2.0. Commit strategy is set to accumulated commits (which is, where the actual change from 2.2.0-> 2.2.1 is).
Jenkins is hosted on a Windows 8.1 machine where builds and tests are performed as well.
The build execution is done on the Jenkins server and no build slaves are used. Only git is used as the SCM (with only one repository) and the current version (1.9.5) of git is used. The cmd version of the git.exe is used (in order to work with ssh properly) according to these instructions: http://opensourcetester.co.uk/2013/06/28/jenkins-windows-ssh/