Ensure we get all tags during initial clone
Ensure we get all tags during initial clone

If a tag is not on the master branch then its ref will not be visible after the initial clone.

A repeat of swift-build after such a failure would execute a `git fetch` on the clone thus fetching that tag.

This diff makes the behavior the same for both paths.

Fixes rdar://problem/23666291

mxcl/swift-package-manager,vmanot/swift-package-manager,abertelrud/swift-package-manager,sschiau/swift-package-manager,mxcl/swift-package-manager,rsmoz/swift-package-manager,sschiau/swift-package-manager,haskellswift/swift-package-manager,mxcl/swift-package-manager,JGiola/swift-package-manager,vmanot/swift-package-manager,vmanot/swift-package-manager,apple/swift-package-manager,sschiau/swift-package-manager,haskellswift/swift-package-manager,haskellswift/swift-package-manager,sschiau/swift-package-manager,apple/swift-package-manager,rsmoz/swift-package-manager,JGiola/swift-package-manager,abertelrud/swift-package-manager,JGiola/swift-package-manager,abertelrud/swift-package-manager,apple/swift-package-manager,abertelrud/swift-package-manager,vmanot/swift-package-manager,haskellswift/swift-package-manager,abertelrud/swift-package-manager,JGiola/swift-package-manager,sschiau/swift-package-manager,JGiola/swift-package-manager,vmanot/swift-package-manager,apple/swift-package-manager,mxcl/swift-package-manager,apple/swift-package-manager