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SaltStack provides "versioned" repositories, this commit add a way to set which release of salt to use. It adds a pillar "salt:release" which can be set to a specific release (ex: 2016.11). This release is then used to configure properly the repositories URLs for Debian/Ubuntu/RedHat. The default behavior is to point to 'latest', retaining the previous behavior if the "salt:release" pillar is not set.