Allow the user to set alternative to ~/.bundle

Recognize new environment variables, with the following fallbacks:

    $BUNDLE_USER_HOME   -> $HOME/.bundle
    $BUNDLE_USER_CACHE  -> $BUNDLE_USER_HOME/cache
    $BUNDLE_USER_CONFIG -> $BUNDLE_USER_HOME/config
    $BUNDLE_USER_PLUGIN -> $BUNDLE_USER_HOME/plugin

TODOs:
- Error handling in Bundler.user_bundle_path when an invalid option is
passed
- Add tests (see https://github.com/bundler/bundler/pull/5787/commits/47fbe99387fea73fa652ad6692349b24cad6fe2e)
- Draft PR with reference to GitHub issue numbers (not linked here as
per contributing guidelines)
    + Issue: 4333
    + Pull request: 5787

1 files changed, 19 insertions, 2 deletions

diff --git a/lib/bundler.rb b/lib/bundler.rb
index 81c6a5b594..31602dfa65 100644
--- a/lib/bundler.rb
+++ b/lib/bundler.rb
@@ -193,10 +193,27 @@ module Bundler
       raise e.exception("#{warning}\nBundler also failed to create a temporary home directory at `#{path}':\n#{e}")
     end
 
-    def user_bundle_path
+    def user_bundle_path_default
       Pathname.new(user_home).join(".bundle")
     end
 
+    def user_bundle_path(dir="home")
+      # if "home", user_bundle_path_default
+      env_var, fallback = case dir
+                when "home"
+                  ["BUNDLE_USER_HOME", user_bundle_path_default]
+                when "cache"
+                  ["BUNDLE_USER_CACHE", user_bundle_path.join("cache")]
+                when "config"
+                  ["BUNDLE_USER_CONFIG", user_bundle_path.join("config")]
+                when "plugin"
+                  ["BUNDLE_USER_PLUGIN", user_bundle_path.join("plugin")]
+                else
+                  nil
+                end
+      ENV.fetch(env_var, fallback)
+    end
+
     def home
       bundle_path.join("bundler")
     end
@@ -210,7 +227,7 @@ module Bundler
     end
 
     def user_cache
-      user_bundle_path.join("cache")
+      user_bundle_path("cache")
     end
 
     def root