Load gemspec file at that directory

Gemspec files generated by old bundler run `git` without changing the
working directory.
Or some gemspec files expect an owned file at the top exists ath the
current working directory.

1 files changed, 2 insertions, 2 deletions

diff --git a/tool/lib/bundled_gem.rb b/tool/lib/bundled_gem.rb
index 0b7d52b86a..38c331183d 100644
--- a/tool/lib/bundled_gem.rb
+++ b/tool/lib/bundled_gem.rb
@@ -15,8 +15,8 @@ module BundledGem
   end
 
   def copy(path, *rest)
-    spec = Gem::Specification.load(path)
-    path = File.dirname(path)
+    path, n = File.split(path)
+    spec = Dir.chdir(path) {Gem::Specification.load(n)} or raise "Cannot load #{path}"
     prepare_test(spec, *rest) do |dir|
       FileUtils.rm_rf(dir)
       files = spec.files.reject {|f| f.start_with?(".git")}