Resolve relative paths in the Include directive properly

According to ssh_config(5), relative paths in the Include directive is
relative from the directory of the root file, not from that of the
including file.  If `~/.ssh/config` includes `~/.ssh/dir1/file1` which
has a line `Include dir2/file2`, ssh tries to include
`~/.ssh/dir2/file2`, not `~/.ssh/dir1/dir2/file2`.

lib/net/ssh/config.rb

@@ -72,9 +72,9 @@ def for(host, files=expandable_default_files)
       # ones. Returns a hash containing the OpenSSH options. (See
       # #translate for how to convert the OpenSSH options into Net::SSH
       # options.)
-      def load(path, host, settings={})
+      def load(path, host, settings={}, base_dir = nil)
         file = File.expand_path(path)
-        base_dir = File.dirname(file)
+        base_dir ||= File.dirname(file)
         return settings unless File.readable?(file)
 
         globals = {}
@@ -125,7 +125,7 @@ def load(path, host, settings={})
               (globals[key] ||= []) << value
             when 'include'
               included_file_paths(base_dir, value).each do |file_path|
-                globals = load(file_path, host, globals)
+                globals = load(file_path, host, globals, base_dir)
               end
             else
               globals[key] = value unless settings.key?(key)
@@ -136,7 +136,7 @@ def load(path, host, settings={})
               (settings[key] ||= []) << value
             when 'include'
               included_file_paths(base_dir, value).each do |file_path|
-                settings = load(file_path, host, settings)
+                settings = load(file_path, host, settings, base_dir)
               end
             else
               settings[key] = value unless settings.key?(key)
@@ -304,9 +304,7 @@ def merge_challenge_response_with_keyboard_interactive(hash)
         end
 
         def included_file_paths(base_dir, config_path)
-          paths = Dir.glob(File.expand_path(config_path)).select { |f| File.file?(f) }
-          paths += Dir.glob(File.join(base_dir, config_path)).select { |f| File.file?(f) }
-          paths.uniq
+          Dir.glob(File.expand_path(config_path, base_dir)).select { |f| File.file?(f) }
         end
 
     end