Improve changelog diffs (#5716)
Improve changelog diffs (#5716)

In the case of both branches/tags sharing the same base, it doesn't
really matter. But when it comes to diffs that don't share the same
base, major releases for example, a direct diff is more useful. See
https://goo.gl/cHW4Ym for more.
mrjman/activeadmin,deivid-rodriguez/activeadmin,vraravam/activeadmin,deivid-rodriguez/activeadmin,javierjulio/activeadmin,javierjulio/activeadmin,mrjman/activeadmin,activeadmin/activeadmin,vraravam/activeadmin,vraravam/activeadmin,javierjulio/activeadmin,activeadmin/activeadmin,mrjman/activeadmin,activeadmin/activeadmin,deivid-rodriguez/activeadmin