$NetBSD: patch-lib_rubygems_installer.rb,v 1.2 2015/03/08 15:08:33 taca Exp $

* Add install_root option for pkgsrc's rubygems support.
* Tweak build_info directory with destdir to store build_args.

--- lib/rubygems/installer.rb.orig	2014-02-06 02:59:36.000000000 +0000
+++ lib/rubygems/installer.rb
@@ -94,6 +94,9 @@ class Gem::Installer
   #                      If your Ruby is ruby18, foo_exec will be installed as
   #                      foo_exec18.
   # :ignore_dependencies:: Don't raise if a dependency is missing.
+  # :install_root:: The directory to use as a buildroot for "destdir"-style
+  #		  installation.  All paths during installation are relative
+  #               to the buildroot.
   # :install_dir:: The directory to install the gem into.
   # :security_policy:: Use the specified security policy.  See Gem::Security
   # :user_install:: Indicate that the gem should be unpacked into the users
@@ -588,7 +591,13 @@ class Gem::Installer
     # If the user has asked for the gem to be installed in a directory that is
     # the system gem directory, then use the system bin directory, else create
     # (or use) a new bin dir under the gem_home.
-    @bin_dir             = options[:bin_dir] || Gem.bindir(gem_home)
+    install_root         = options[:install_root]
+    @bin_dir             = options[:bin_dir] || Gem.bindir(gem_home, install_root)
+    @development         = options[:development]
+    unless install_root.nil? or install_root.empty?
+      @install_root = File.expand_path install_root
+      @gem_home = File.join(@install_root, @gem_home)
+    end
     @development         = options[:development]
 
     @build_args          = options[:build_args] || Gem::Command.build_args
@@ -769,6 +778,9 @@ TEXT
     return if @build_args.empty?
 
     build_info_dir = File.join gem_home, 'build_info'
+    unless @install_root.nil? or @install_root.empty?
+      build_info_dir = File.join @gem_home, "build_info"
+    end
 
     FileUtils.mkdir_p build_info_dir