core: expand Windows short paths

lib/vagrant/util/platform.rb

@@ -117,6 +117,14 @@ module Vagrant
           path = Pathname.new(File.expand_path(path))
 
           if path.exist? && !fs_case_sensitive?
+            # If the path contains a Windows short path, then we attempt to
+            # expand. The require below is embedded here since it requires
+            # windows to work.
+            if windows? && path.to_s =~ /~\d(\/|\\)/
+              require_relative "windows_path"
+              path = Pathname.new(WindowsPath.longname(path.to_s))
+            end
+
             # Build up all the parts of the path
             original = []
             while !path.root?

lib/vagrant/util/windows_path.rb

@@ -0,0 +1,38 @@
+require "fiddle/import"
+
+module Vagrant
+  module Util
+    module WindowsPath
+      module API
+        extend Fiddle::Importer
+        dlload 'kernel32.dll'
+        extern("int GetLongPathNameA(char*, char*, int)", :stdcall)
+      end
+
+      # Converts a Windows shortname to a long name. This only works
+      # for ASCII paths currently and doesn't use the wide character
+      # support.
+      def self.longname(name)
+        # We loop over the API call in case we didn't allocate enough
+        # buffer space. In general it is usually enough.
+        bufferlen = 250
+        buffer    = nil
+        while true
+          buffer = ' ' * bufferlen
+          len    = API.GetLongPathNameA(name.to_s, buffer, buffer.size)
+          if bufferlen < len
+            # If the length returned is larger than our buffer length,
+            # it is the API telling us it needs more space. Allocate it
+            # and retry.
+            bufferlen = len
+            continue
+          end
+
+          break
+        end
+
+        return buffer.rstrip.chomp("\0")
+      end
+    end
+  end
+end