Make install --path relative to the cwd

lib/bundler/cli/install.rb

@@ -170,7 +170,7 @@ def normalize_groups
     def normalize_settings
       Bundler.settings.set_command_option :path, nil if options[:system]
       Bundler.settings.set_command_option :path, "vendor/bundle" if options[:deployment]
-      Bundler.settings.set_command_option_if_given :path, options["path"]
+      Bundler.settings.set_command_option :path, Bundler.feature_flag.path_relative_to_cwd? ? File.expand_path(options["path"]) : options["path"] if options["path"]
       Bundler.settings.set_command_option :path, "bundle" if options["standalone"] && Bundler.settings[:path].nil?
 
       bin_option = options["binstubs"]

lib/bundler/feature_flag.rb

@@ -44,6 +44,7 @@ def self.settings_method(name, key, &default)
     settings_flag(:list_command) { bundler_2_mode? }
     settings_flag(:lockfile_uses_separate_rubygems_sources) { bundler_2_mode? }
     settings_flag(:only_update_to_newer_versions) { bundler_2_mode? }
+    settings_flag(:path_relative_to_cwd) { bundler_2_mode? }
     settings_flag(:plugins) { @bundler_version >= Gem::Version.new("1.14") }
     settings_flag(:prefer_gems_rb) { bundler_2_mode? }
     settings_flag(:print_only_version_number) { bundler_2_mode? }

lib/bundler/settings.rb

@@ -43,6 +43,7 @@ class Settings
       no_install
       no_prune
       only_update_to_newer_versions
+      path_relative_to_cwd
       path.system
       plugins
       prefer_gems_rb

man/bundle-config.ronn

@@ -218,6 +218,8 @@ learn more about their operation in [bundle install(1)][bundle-install].
    is used, defaults to vendor/bundle.
 * `path.system` (`BUNDLE_PATH__SYSTEM`):
    Whether Bundler will install gems into the default system path (`Gem.dir`).
+* `path_relative_to_cwd` (`PATH_RELATIVE_TO_CWD`)
+   Makes `--path` relative to the CWD instead of the `Gemfile`.
 * `plugins` (`BUNDLE_PLUGINS`):
    Enable Bundler's experimental plugin system.
 * `prefer_gems_rb` (`BUNDLE_PREFER_GEMS_RB`)

spec/install/path_spec.rb

@@ -49,6 +49,18 @@
       expect(vendored_gems("gems/rack-1.0.0")).to be_directory
       expect(the_bundle).to include_gems "rack 1.0.0"
     end
+
+    context "with path_relative_to_cwd set to true" do
+      before { bundle! "config path_relative_to_cwd true" }
+
+      it "installs the bundle relatively to current working directory" do
+        Dir.chdir(bundled_app.parent) do
+          bundle "install --gemfile='#{bundled_app}/Gemfile' --path vendor/bundle"
+          expect(out).to include("installed into ./vendor/bundle")
+          expect(Dir.exist?("vendor/bundle")).to be true
+        end
+      end
+    end
   end
 
   describe "when BUNDLE_PATH or the global path config is set" do