[bundler/bundler] Fix file:// handling under Windows

Windows paths do not start with a slash, so we add an extra slash to
separate the host from the path in file:// urls. Otherwise "D:" is
parsed as the host segment in the URI.

The path for those URLs now starts with "/", so we ignore that leading
character when using the URI's path.

This reduces Windows CI spec failures from 429 to 355.

https://github.com/bundler/bundler/commit/1b7e274cbc

lib/bundler/fetcher.rb

@@ -99,7 +99,8 @@ module Bundler
 
       uri = URI.parse("#{remote_uri}#{Gem::MARSHAL_SPEC_DIR}#{spec_file_name}.rz")
       if uri.scheme == "file"
-        Bundler.load_marshal Bundler.rubygems.inflate(Gem.read_binary(uri.path))
+        path = Gem.win_platform? ? uri.path[1..-1] : uri.path
+        Bundler.load_marshal Bundler.rubygems.inflate(Gem.read_binary(path))
       elsif cached_spec_path = gemspec_cached_path(spec_file_name)
         Bundler.load_gemspec(cached_spec_path)
       else

lib/bundler/fetcher/index.rb

@@ -30,7 +30,8 @@ module Bundler
 
         uri = URI.parse("#{remote_uri}#{Gem::MARSHAL_SPEC_DIR}#{spec_file_name}.rz")
         if uri.scheme == "file"
-          Bundler.load_marshal Bundler.rubygems.inflate(Gem.read_binary(uri.path))
+          path = Gem.win_platform? ? uri.path[1..-1] : uri.path
+          Bundler.load_marshal Bundler.rubygems.inflate(Gem.read_binary(path))
         elsif cached_spec_path = gemspec_cached_path(spec_file_name)
           Bundler.load_gemspec(cached_spec_path)
         else

spec/bundler/support/path.rb

@@ -64,10 +64,11 @@ module Spec
 
     def file_uri_for(path)
       protocol = "file://"
+      root = Gem.win_platform? ? "/" : ""
 
-      return protocol + "localhost" + path.to_s if RUBY_VERSION < "2.5"
+      return protocol + "localhost" + root + path.to_s if RUBY_VERSION < "2.5"
 
-      protocol + path.to_s
+      protocol + root + path.to_s
     end
 
     def gem_repo1(*args)