In some cases, changelog or release notes do not need to be compiled for
various reasons.
This commit adds an option to Skip building the changelog.
Fix#888
When Jenkins is configured with 'Check out to matching local branch' the branch and tag name will conflict.
If we use explicit references to tags, then life is much better.
This patch also replaces our manual 'tag or not' boolean with a regex to check if the return is a SHA1.
If it is not a SHA1, it is assumed to be a tag. Hopefully this helps with future maintainability.
