Ability to run a 'dry-run'

[DovetailJohn]

As part of our release process we would like to be able to pull a list of issues that would be included in the next release. This would pull the same release notes but not write them to a tag, I guess the tag would not have to exist so we would need to pull all closed issues since the previous tag until an end date of now.

I'll be glad to submit a PR if you can give me some direction/comments.

[GlennM]

Nice suggestion :)