Throw JGit exception when ResetCommand got wrong ref
If the ResetCommand should reset to a invalid ref (e.g. HEAD in a repo
whithout a single commit) it was throwing an NPE. This is fixed now by
throwing a JGitInternalExcpeption. It would be nicer if we could throw
a InvalidRefException, but this would modify our API.
Bug: 339610
Change-Id: Iffcb4f2cca9f702176471d93c3a71e5cb3e700b1 Signed-off-by: Christian Halstrick <christian.halstrick@sap.com> Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>