I may have missed a flag or something, but this doesn't appear to support release histories that include multiple maintained release branches.

As an example, see the changelog generated for github.com/pilosa/pilosa: https://gist.github.com/codysoyland/703101d5be09fc811cb3f7a6ab8d1e8e

As you can see, we made releases in the following order:

1. 0.2.4
2. 0.3.1
3. 0.2.5
4. 0.3.2

However, the changelog assumes that each of these releases was an evolution from the previous by order of date. But we are actually maintaining two release branches, a 0.2.x branch and a 0.3.x branch.

In other words, the previous version that is used to generate the change list and diff link should not be the previous tag by date, but the most recent tagged ancestor in git history.