[rubygems/rubygems] Copy template contents instead of file and perms

This allows the file to be created without copying permissions
from Bundler's installation source. The previous behaviour was
noticed after installing Ruby through brew, and using bundle
init, which yielded a read-only Gemfile.

https://github.com/rubygems/rubygems/commit/839a06851d

lib/bundler/cli/init.rb

@@ -32,7 +32,11 @@ module Bundler
           file << spec.to_gemfile
         end
       else
-        FileUtils.cp(File.expand_path("../templates/#{gemfile}", __dir__), gemfile)
+        File.open(File.expand_path("../templates/#{gemfile}", __dir__), "r") do |template|
+          File.open(gemfile, "wb") do |destination|
+            IO.copy_stream(template, destination)
+          end
+        end
       end
 
       puts "Writing new #{gemfile} to #{SharedHelpers.pwd}/#{gemfile}"

spec/bundler/commands/init_spec.rb

@@ -7,6 +7,29 @@ RSpec.describe "bundle init" do
     expect(bundled_app_gemfile).to be_file
   end
 
+  context "with a template with permission flags not matching current process umask" do
+    let(:template_file) do
+      gemfile = Bundler.preferred_gemfile_name
+      templates_dir.join(gemfile)
+    end
+
+    let(:target_dir) { bundled_app("init_permissions_test") }
+
+    around do |example|
+      old_chmod = File.stat(template_file).mode
+      FileUtils.chmod(old_chmod | 0o111, template_file) # chmod +x
+      example.run
+      FileUtils.chmod(old_chmod, template_file)
+    end
+
+    it "honours the current process umask when generating from a template" do
+      FileUtils.mkdir(target_dir)
+      bundle :init, :dir => target_dir
+      generated_mode = File.stat(File.join(target_dir, "Gemfile")).mode & 0o111
+      expect(generated_mode).to be_zero
+    end
+  end
+
   context "when a Gemfile already exists" do
     before do
       create_file "Gemfile", <<-G

spec/bundler/support/path.rb

@@ -312,6 +312,10 @@ module Spec
       source_root.join("tool/bundler")
     end
 
+    def templates_dir
+      lib_dir.join("bundler", "templates")
+    end
+
     extend self
   end
 end