Merge pull request #3988 from voxik/fix-file-not-found-gemspec-gemspec

Append '.gemspec' extension only when it is not present.

(cherry picked from commit 214fefc)

Author: deivid-rodriguez

lib/rubygems/commands/build_command.rb

@@ -79,7 +79,7 @@ def find_gemspec
   end
 
   def build_gem(gem_name)
-    gemspec = File.exist?(gem_name) ? gem_name : "#{gem_name}.gemspec"
+    gemspec = File.extname(gem_name) == ".gemspec" ? gem_name : "#{gem_name}.gemspec"
 
     if File.exist?(gemspec)
       spec = Gem::Specification.load(gemspec)

test/rubygems/test_gem_commands_build_command.rb

@@ -273,7 +273,7 @@ def test_execute_outside_dir
   end
 
   def test_can_find_gemspecs_without_dot_gemspec
-    gemspec_file = File.join(@tempdir, @gem.spec_name)
+    gemspec_file = File.join(@tempdir, @gem.name)
 
     File.open gemspec_file + ".gemspec", 'w' do |gs|
       gs.write @gem.to_ruby