Fix otrs-3773 : 'Weird behavior of the "Compare with branch" feature'.

Issue subversive#484929: https://bugs.eclipse.org/bugs/show_bug.cgi?id=484929
Backported from 3.0.3 to 2.0.4.

git-svn-id: https://dev.eclipse.org/svnroot/technology/org.eclipse.subversive/tags/2.0.4.I20150123-1700@21465 ee007c2a-0a25-0410-9ab9-bf268980928c