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[synth]

Hi. Thanks for this gem!

One thing I noticed is that this is centered around pull requests and doesn't work very well for generating releases that have commits that are not in pull requests.

I forked and added the ability to create releases that have autogenerated changelogs based on the most recent commit and the previous release. See here: https://github.com/synth/capistrano-github-releases/commit/a3003d54f21e652d2bee7833a563fb4c0245ea1c

This now works really well for my case, but breaks the existing pull request behavior, so I just removed it in my fork. Before I create a PR, I wanted to just throw this out there and see if you were interested in merging this behavior and if so, what strategy would you like to take.