[rubygems/rubygems] Fix path vs deployment precedence when path set through ENV

The `deployment` setting sets `path` to `vendor/bundle` implicitly, but
that should only apply if `path` is not set explicitly, at any level.

https://github.com/rubygems/rubygems/commit/3552c064c1

lib/bundler/settings.rb

@@ -219,7 +219,6 @@ module Bundler
     def path
       configs.each do |_level, settings|
         path = value_for("path", settings)
-        path = "vendor/bundle" if value_for("deployment", settings) && path.nil?
         path_system = value_for("path.system", settings)
         disabled_shared_gems = value_for("disable_shared_gems", settings)
         next if path.nil? && path_system.nil? && disabled_shared_gems.nil?
@@ -227,7 +226,9 @@ module Bundler
         return Path.new(path, system_path)
       end
 
-      Path.new(nil, false)
+      path = "vendor/bundle" if self[:deployment]
+
+      Path.new(path, false)
     end
 
     Path = Struct.new(:explicit_path, :system_path) do

spec/bundler/install/deploy_spec.rb

@@ -248,6 +248,12 @@ RSpec.describe "install in deployment or frozen mode" do
       expect(out).to include("vendor/bundle2")
     end
 
+    it "installs gems to custom path if specified, even when configured through ENV" do
+      bundle "config set deployment true"
+      bundle "install", :env => { "BUNDLE_PATH" => "vendor/bundle2" }
+      expect(out).to include("vendor/bundle2")
+    end
+
     it "works with the `frozen` setting" do
       bundle "config set frozen true"
       bundle "install"