[rubygems/rubygems] Centralize logic using `Pathname#relative_path_from`

To avoid potential crashes when trying to jump from a drive to another
on Windows, and take the change refactor things a bit.

https://github.com/rubygems/rubygems/commit/7c9a9a431a

lib/bundler/cli/check.rb

@@ -29,7 +29,7 @@ module Bundler
         Bundler.ui.warn "Install missing gems with `bundle install`"
         exit 1
       elsif !Bundler.default_lockfile.file? && Bundler.frozen_bundle?
-        Bundler.ui.error "This bundle has been frozen, but there is no #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)} present"
+        Bundler.ui.error "This bundle has been frozen, but there is no #{SharedHelpers.relative_lockfile_path} present"
         exit 1
       else
         Bundler.load.lock(:preserve_unknown_sections => true) unless options[:"dry-run"]

lib/bundler/cli/install.rb

@@ -29,7 +29,7 @@ module Bundler
           flag ||= "--frozen flag"     if options[:frozen]
           flag ||= "deployment setting"
           raise ProductionError, "The #{flag} requires a lockfile. Please make " \
-                                 "sure you have checked your #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)} into version control " \
+                                 "sure you have checked your #{SharedHelpers.relative_lockfile_path} into version control " \
                                  "before deploying."
         end
 

lib/bundler/definition.rb

@@ -405,13 +405,13 @@ module Bundler
       msg << "\n\nYou have added to the Gemfile:\n" << added.join("\n") if added.any?
       msg << "\n\nYou have deleted from the Gemfile:\n" << deleted.join("\n") if deleted.any?
       msg << "\n\nYou have changed in the Gemfile:\n" << changed.join("\n") if changed.any?
-      msg << "\n\nRun `bundle install` elsewhere and add the updated #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)} to version control.\n"
+      msg << "\n\nRun `bundle install` elsewhere and add the updated #{SharedHelpers.relative_gemfile_path} to version control.\n"
 
       unless explicit_flag
         suggested_command = unless Bundler.settings.locations("frozen").keys.include?(:env)
           "bundle config set frozen false"
         end
-        msg << "If this is a development machine, remove the #{Bundler.default_gemfile.relative_path_from(SharedHelpers.pwd)} " \
+        msg << "If this is a development machine, remove the #{SharedHelpers.relative_lockfile_path} " \
                "freeze by running `#{suggested_command}`." if suggested_command
       end
 

lib/bundler/env.rb

@@ -40,11 +40,11 @@ module Bundler
 
         out << "\n## Gemfile\n"
         gemfiles.each do |gemfile|
-          out << "\n### #{Pathname.new(gemfile).relative_path_from(SharedHelpers.pwd)}\n\n"
+          out << "\n### #{SharedHelpers.relative_path_to(gemfile)}\n\n"
           out << "```ruby\n" << read_file(gemfile).chomp << "\n```\n"
         end
 
-        out << "\n### #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)}\n\n"
+        out << "\n### #{SharedHelpers.relative_path_to(Bundler.default_lockfile)}\n\n"
         out << "```\n" << read_file(Bundler.default_lockfile).chomp << "\n```\n"
       end
 

lib/bundler/installer/standalone.rb

@@ -55,20 +55,13 @@ module Bundler
       if spec.source.instance_of?(Source::Path) && spec.source.path.absolute?
         full_path
       else
-        relative_path_from(Bundler.root.join(bundler_path), :to => full_path) || full_path
+        SharedHelpers.relative_path_to(full_path, :from => Bundler.root.join(bundler_path))
       end
     rescue TypeError
       error_message = "#{spec.name} #{spec.version} has an invalid gemspec"
       raise Gem::InvalidSpecificationException.new(error_message)
     end
 
-    def relative_path_from(source, to:)
-      Pathname.new(to).relative_path_from(source).to_s
-    rescue ArgumentError
-      # on Windows, if source and destination are on different drivers, there's no relative path from one to the other
-      nil
-    end
-
     def define_path_helpers
       <<~'END'
         unless defined?(Gem)

lib/bundler/lockfile_parser.rb

@@ -68,7 +68,7 @@ module Bundler
 
       if lockfile.match?(/<<<<<<<|=======|>>>>>>>|\|\|\|\|\|\|\|/)
         raise LockfileError, "Your lockfile contains merge conflicts.\n" \
-          "Run `git checkout HEAD -- #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)}` first to get a clean lock."
+          "Run `git checkout HEAD -- #{SharedHelpers.relative_lockfile_path}` first to get a clean lock."
       end
 
       lockfile.split(/(?:\r?\n)+/) do |line|
@@ -92,7 +92,7 @@ module Bundler
       @specs = @specs.values.sort_by!(&:full_name)
     rescue ArgumentError => e
       Bundler.ui.debug(e)
-      raise LockfileError, "Your lockfile is unreadable. Run `rm #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)}` " \
+      raise LockfileError, "Your lockfile is unreadable. Run `rm #{SharedHelpers.relative_lockfile_path}` " \
         "and then `bundle install` to generate a new lockfile."
     end
 

lib/bundler/shared_helpers.rb

@@ -197,6 +197,21 @@ module Bundler
       filesystem_access(gemfile_path) {|g| File.open(g, "w") {|file| file.puts contents } }
     end
 
+    def relative_gemfile_path
+      relative_path_to(Bundler.default_gemfile)
+    end
+
+    def relative_lockfile_path
+      relative_path_to(Bundler.default_lockfile)
+    end
+
+    def relative_path_to(destination, from: pwd)
+      Pathname.new(destination).relative_path_from(from).to_s
+    rescue ArgumentError
+      # on Windows, if source and destination are on different drivers, there's no relative path from one to the other
+      destination
+    end
+
     private
 
     def validate_bundle_path