Require spec path helpers lazily in the git config guard

support/subprocess.rb is preloaded into every spawned ruby before
RubygemsVersionManager switches RubyGems, and requiring support/path at
load time dragged the pathname default gem into that context, breaking
Bundler unit specs under a ruby-core setup. Require it only when a
local git config write actually needs the tmp root check.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: hsbt

spec/support/subprocess.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require_relative "command_execution"
-require_relative "path"
 
 module Spec
   module Subprocess
@@ -47,6 +46,10 @@ def reject_git_config_pollution!(cmd, path)
       return if args.any? {|a| ["--global", "--system", "-f", "--file"].include?(a) || a.start_with?("--file=") }
       return if args.any? {|a| ["--get", "--get-all", "--get-regexp", "--get-urlmatch", "--list", "-l"].include?(a) }
 
+      # Required lazily because this file is loaded in every spawned ruby
+      # before RubygemsVersionManager switches RubyGems, where loading extra
+      # default gems (pathname, through support/path) breaks the setup.
+      require_relative "path"
       dir = File.expand_path(path.to_s)
       tmp_root = Spec::Path.tmp_root.to_s
       return if dir == tmp_root || dir.start_with?(tmp_root + File::SEPARATOR)