AppVeyor builds all branches per default. Add a configuration setting to only build the master branch. See http://www.appveyor.com/docs/branches#white-and-blacklisting for details. For the record, AppVeyor builds can skipped by annotating the commit message according to http://www.appveyor.com/docs/how-to/skip-build Useful for e.g. website commits. [skip appveyor]
Packer lacks an official Windows CI server. This commit adds a configuration file for AppVeyor, which is a Windows CI service (free for open-source projects).