Auto merge of #6628 - bundler:segiddins/bundler-2-global-path-ruby-sc…

…ope, r=indirect

[Settings] Append the ruby scope on Bundler 2 with a global path setting

### What was the end-user problem that led to this PR?

The problem was `bundle config path` behaving differently depending on whether the config is local or global was... confusing.

Closes #6619 (comment).

### What was your diagnosis of the problem?

My diagnosis was setting the `path` setting should be consistent, regardless of the level of configuration it is set at.

### What is your fix for the problem, implemented in this PR?

My fix appends the "ruby scope" to the path when set globally on Bundler 2.

### Why did you choose this fix out of the possible options?

I chose this fix because it means users won't have to re-install gems when switching rubies with a global `BUNDLE_PATH` set.

lib/bundler/feature_flag.rb

@@ -39,6 +39,7 @@ def self.settings_method(name, key, &default)
     settings_flag(:disable_multisource) { bundler_2_mode? }
     settings_flag(:error_on_stderr) { bundler_2_mode? }
     settings_flag(:forget_cli_options) { bundler_2_mode? }
+    settings_flag(:global_path_appends_ruby_scope) { bundler_2_mode? }
     settings_flag(:global_gem_cache) { bundler_2_mode? }
     settings_flag(:init_gems_rb) { bundler_2_mode? }
     settings_flag(:list_command) { bundler_2_mode? }

lib/bundler/settings.rb

@@ -35,6 +35,7 @@ class Settings
       frozen
       gem.coc
       gem.mit
+      global_path_appends_ruby_scope
       global_gem_cache
       ignore_messages
       init_gems_rb
@@ -225,7 +226,7 @@ def path
       key  = key_for(:path)
       path = ENV[key] || @global_config[key]
       if path && !@temporary.key?(key) && !@local_config.key?(key)
-        return Path.new(path, false, false, false)
+        return Path.new(path, Bundler.feature_flag.global_path_appends_ruby_scope?, false, false)
       end
 
       system_path = self["path.system"] || (self[:disable_shared_gems] == false)

man/bundle-config.ronn

@@ -198,6 +198,9 @@ learn more about their operation in [bundle install(1)](bundle-install.1.html).
 * `global_gem_cache` (`BUNDLE_GLOBAL_GEM_CACHE`):
    Whether Bundler should cache all gems globally, rather than locally to the
    installing Ruby installation.
+* `global_path_appends_ruby_scope` (`BUNDLE_GLOBAL_PATH_APPENDS_RUBY_SCOPE`):
+   Whether Bundler should append the Ruby scope (e.g. engine and ABI version)
+   to a globally-configured path.
 * `ignore_messages` (`BUNDLE_IGNORE_MESSAGES`): When set, no post install
    messages will be printed. To silence a single gem, use dot notation like
    `ignore_messages.httparty true`.