diff --git a/lib/bundler/bundler.gemspec b/lib/bundler/bundler.gemspec
index 48410e76f4..f6cb02cea2 100644
--- a/lib/bundler/bundler.gemspec
+++ b/lib/bundler/bundler.gemspec
@@ -34,11 +34,14 @@ Gem::Specification.new do |s|
   s.required_ruby_version     = ">= 2.3.0"
   s.required_rubygems_version = ">= 2.5.2"
 
-  s.files = (Dir.glob("lib/bundler/**/*", File::FNM_DOTMATCH) + Dir.glob("man/bundle*") + Dir.glob("man/gemfile*") + Dir.glob("libexec/bundle*")).reject {|f| File.directory?(f) }
+  s.files = Dir.glob("{lib,exe}/**/*", File::FNM_DOTMATCH).reject {|f| File.directory?(f) }
 
-  s.files += ["lib/bundler.rb"]
+  # Include the CHANGELOG.md, LICENSE.md, README.md manually
+  s.files += %w[CHANGELOG.md LICENSE.md README.md]
+  # include the gemspec itself because warbler breaks w/o it
+  s.files += %w[bundler.gemspec]
 
-  s.bindir        = "libexec"
+  s.bindir        = "exe"
   s.executables   = %w[bundle bundler]
   s.require_paths = ["lib"]
 end
diff --git a/lib/bundler/cli.rb b/lib/bundler/cli.rb
index 421f42cb52..981c885f6f 100644
--- a/lib/bundler/cli.rb
+++ b/lib/bundler/cli.rb
@@ -591,6 +591,7 @@ module Bundler
                          :desc => "Generate a test directory for your library, either rspec, minitest or test-unit. Set a default with `bundle config set --global gem.test (rspec|minitest|test-unit)`."
     method_option :ci, :type => :string, :lazy_default => Bundler.settings["gem.ci"] || "",
                        :desc => "Generate CI configuration, either GitHub Actions, Travis CI, GitLab CI or CircleCI. Set a default with `bundle config set --global gem.ci (github|travis|gitlab|circle)`"
+    method_option :github_username, :type => :string, :default => Bundler.settings["gem.github_username"], :banner => "Set your username on GitHub", :desc => "Fill in GitHub username on README so that you don't have to do it manually. Set a default with `bundle config set --global gem.github_username <your_username>`."
 
     def gem(name)
     end
diff --git a/lib/bundler/cli/common.rb b/lib/bundler/cli/common.rb
index 23ac78a103..32d952fb72 100644
--- a/lib/bundler/cli/common.rb
+++ b/lib/bundler/cli/common.rb
@@ -36,10 +36,15 @@ module Bundler
     def self.without_groups_message(command)
       command_in_past_tense = command == :install ? "installed" : "updated"
       groups = Bundler.settings[:without]
+      "Gems in the #{verbalize_groups(groups)} were not #{command_in_past_tense}."
+    end
+
+    def self.verbalize_groups(groups)
+      groups.map!{|g| "'#{g}'" }
       group_list = [groups[0...-1].join(", "), groups[-1..-1]].
         reject {|s| s.to_s.empty? }.join(" and ")
       group_str = groups.size == 1 ? "group" : "groups"
-      "Gems in the #{group_str} #{group_list} were not #{command_in_past_tense}."
+      "#{group_str} #{group_list}"
     end
 
     def self.select_spec(name, regex_match = nil)
@@ -53,7 +58,13 @@ module Bundler
 
       case specs.count
       when 0
-        raise GemNotFound, gem_not_found_message(name, Bundler.definition.dependencies)
+        dep_in_other_group = Bundler.definition.current_dependencies.find {|dep|dep.name == name }
+
+        if dep_in_other_group
+          raise GemNotFound, "Could not find gem '#{name}', because it's in the #{verbalize_groups(dep_in_other_group.groups)}, configured to be ignored."
+        else
+          raise GemNotFound, gem_not_found_message(name, Bundler.definition.dependencies)
+        end
       when 1
         specs.first
       else
diff --git a/lib/bundler/cli/gem.rb b/lib/bundler/cli/gem.rb
index 2c63da9eb4..eb1119859c 100644
--- a/lib/bundler/cli/gem.rb
+++ b/lib/bundler/cli/gem.rb
@@ -42,9 +42,17 @@ module Bundler
       use_git = Bundler.git_present? && options[:git]
 
       git_author_name = use_git ? `git config user.name`.chomp : ""
-      github_username = use_git ? `git config github.user`.chomp : ""
+      git_username = use_git ? `git config github.user`.chomp : ""
       git_user_email = use_git ? `git config user.email`.chomp : ""
 
+      github_username = if options[:github_username].nil?
+        git_username
+      elsif options[:github_username] == false
+        ""
+      else
+        options[:github_username]
+      end
+
       config = {
         :name             => name,
         :underscored_name => underscored_name,
diff --git a/lib/bundler/cli/outdated.rb b/lib/bundler/cli/outdated.rb
index 6a1789e235..e5d9af477c 100644
--- a/lib/bundler/cli/outdated.rb
+++ b/lib/bundler/cli/outdated.rb
@@ -72,7 +72,7 @@ module Bundler
         gemfile_specs + dependency_specs
       end
 
-      specs.sort_by(&:name).each do |current_spec|
+      specs.sort_by(&:name).uniq(&:name).each do |current_spec|
         next unless gems.empty? || gems.include?(current_spec.name)
 
         active_spec = retrieve_active_spec(definition, current_spec)
diff --git a/lib/bundler/definition.rb b/lib/bundler/definition.rb
index 686721cd32..562f50c3fb 100644
--- a/lib/bundler/definition.rb
+++ b/lib/bundler/definition.rb
@@ -187,10 +187,10 @@ module Bundler
           gem_name, gem_version = extract_gem_info(e)
           locked_gem = @locked_specs[gem_name].last
           raise if locked_gem.nil? || locked_gem.version.to_s != gem_version || !@remote
-          raise GemNotFound, "Your bundle is locked to #{locked_gem}, but that version could not " \
-                             "be found in any of the sources listed in your Gemfile. If you haven't changed sources, " \
-                             "that means the author of #{locked_gem} has removed it. You'll need to update your bundle " \
-                             "to a version other than #{locked_gem} that hasn't been removed in order to install."
+          raise GemNotFound, "Your bundle is locked to #{locked_gem} from #{locked_gem.source}, but that version can " \
+                             "no longer be found in that source. That means the author of #{locked_gem} has removed it. " \
+                             "You'll need to update your bundle to a version other than #{locked_gem} that hasn't been " \
+                             "removed in order to install."
         end
         unless specs["bundler"].any?
           bundler = sources.metadata_source.specs.search(Gem::Dependency.new("bundler", VERSION)).last
@@ -959,7 +959,7 @@ module Bundler
     end
 
     def additional_base_requirements_for_resolve
-      return [] unless @locked_gems && Bundler.feature_flag.only_update_to_newer_versions?
+      return [] unless @locked_gems
       dependencies_by_name = dependencies.inject({}) {|memo, dep| memo.update(dep.name => dep) }
       @locked_gems.specs.reduce({}) do |requirements, locked_spec|
         name = locked_spec.name
diff --git a/lib/bundler/feature_flag.rb b/lib/bundler/feature_flag.rb
index a1b443b042..3f9a502179 100644
--- a/lib/bundler/feature_flag.rb
+++ b/lib/bundler/feature_flag.rb
@@ -35,7 +35,6 @@ module Bundler
     settings_flag(:disable_multisource) { bundler_3_mode? }
     settings_flag(:forget_cli_options) { bundler_3_mode? }
     settings_flag(:global_gem_cache) { bundler_3_mode? }
-    settings_flag(:only_update_to_newer_versions) { bundler_3_mode? }
     settings_flag(:path_relative_to_cwd) { bundler_3_mode? }
     settings_flag(:plugins) { @bundler_version >= Gem::Version.new("1.14") }
     settings_flag(:print_only_version_number) { bundler_3_mode? }
diff --git a/lib/bundler/gem_helper.rb b/lib/bundler/gem_helper.rb
index d3e30124f9..6096adfa27 100644
--- a/lib/bundler/gem_helper.rb
+++ b/lib/bundler/gem_helper.rb
@@ -47,6 +47,11 @@ module Bundler
         built_gem_path = build_gem
       end
 
+      desc "Generate SHA512 checksum if #{name}-#{version}.gem into the checksums directory."
+      task "build:checksum" => "build" do
+        build_checksum(built_gem_path)
+      end
+
       desc "Build and install #{name}-#{version}.gem into system gems."
       task "install" => "build" do
         install_gem(built_gem_path)
@@ -100,6 +105,17 @@ module Bundler
       Bundler.ui.confirm "#{name} (#{version}) installed."
     end
 
+    def build_checksum(built_gem_path = nil)
+      built_gem_path ||= build_gem
+      SharedHelpers.filesystem_access(File.join(base, "checksums")) {|p| FileUtils.mkdir_p(p) }
+      file_name = "#{File.basename(built_gem_path)}.sha512"
+      require "digest/sha2"
+      checksum = Digest::SHA512.new.hexdigest(built_gem_path.to_s)
+      target = File.join(base, "checksums", file_name)
+      File.write(target, checksum)
+      Bundler.ui.confirm "#{name} #{version} checksum written to checksums/#{file_name}."
+    end
+
     protected
 
     def rubygem_push(path)
diff --git a/lib/bundler/lazy_specification.rb b/lib/bundler/lazy_specification.rb
index 7cd7e4254d..6760edba42 100644
--- a/lib/bundler/lazy_specification.rb
+++ b/lib/bundler/lazy_specification.rb
@@ -74,9 +74,9 @@ module Bundler
           MatchPlatform.platforms_match?(spec.platform, platform_object)
         end
         installable_candidates = same_platform_candidates.select do |spec|
-          !spec.is_a?(RemoteSpecification) &&
-            spec.required_ruby_version.satisfied_by?(Gem.ruby_version) &&
-            spec.required_rubygems_version.satisfied_by?(Gem.rubygems_version)
+          !spec.is_a?(EndpointSpecification) ||
+            (spec.required_ruby_version.satisfied_by?(Gem.ruby_version) &&
+              spec.required_rubygems_version.satisfied_by?(Gem.rubygems_version))
         end
         search = installable_candidates.last || same_platform_candidates.last
         search.dependencies = dependencies if search && (search.is_a?(RemoteSpecification) || search.is_a?(EndpointSpecification))
diff --git a/lib/bundler/man/bundle-add.1 b/lib/bundler/man/bundle-add.1
index b44295b2d3..ffcd63bbcc 100644
--- a/lib/bundler/man/bundle-add.1
+++ b/lib/bundler/man/bundle-add.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-ADD" "1" "January 2021" "" ""
+.TH "BUNDLE\-ADD" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-add\fR \- Add gem to the Gemfile and run bundle install
diff --git a/lib/bundler/man/bundle-binstubs.1 b/lib/bundler/man/bundle-binstubs.1
index 99876d023e..23c371b7de 100644
--- a/lib/bundler/man/bundle-binstubs.1
+++ b/lib/bundler/man/bundle-binstubs.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-BINSTUBS" "1" "January 2021" "" ""
+.TH "BUNDLE\-BINSTUBS" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-binstubs\fR \- Install the binstubs of the listed gems
diff --git a/lib/bundler/man/bundle-cache.1 b/lib/bundler/man/bundle-cache.1
index 3b3c6f9734..9bb8011a8a 100644
--- a/lib/bundler/man/bundle-cache.1
+++ b/lib/bundler/man/bundle-cache.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-CACHE" "1" "January 2021" "" ""
+.TH "BUNDLE\-CACHE" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-cache\fR \- Package your needed \fB\.gem\fR files into your application
diff --git a/lib/bundler/man/bundle-check.1 b/lib/bundler/man/bundle-check.1
index 4436c3e971..6696479fef 100644
--- a/lib/bundler/man/bundle-check.1
+++ b/lib/bundler/man/bundle-check.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-CHECK" "1" "January 2021" "" ""
+.TH "BUNDLE\-CHECK" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-check\fR \- Verifies if dependencies are satisfied by installed gems
diff --git a/lib/bundler/man/bundle-clean.1 b/lib/bundler/man/bundle-clean.1
index b7e882ecbf..625d87c580 100644
--- a/lib/bundler/man/bundle-clean.1
+++ b/lib/bundler/man/bundle-clean.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-CLEAN" "1" "January 2021" "" ""
+.TH "BUNDLE\-CLEAN" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-clean\fR \- Cleans up unused gems in your bundler directory
diff --git a/lib/bundler/man/bundle-config.1 b/lib/bundler/man/bundle-config.1
index 00bb708240..667249c665 100644
--- a/lib/bundler/man/bundle-config.1
+++ b/lib/bundler/man/bundle-config.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-CONFIG" "1" "January 2021" "" ""
+.TH "BUNDLE\-CONFIG" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-config\fR \- Set bundler configuration options
@@ -199,6 +199,9 @@ The following is a list of all configuration keys and their purpose\. You can le
 \fBfrozen\fR (\fBBUNDLE_FROZEN\fR): Disallow changes to the \fBGemfile\fR\. When the \fBGemfile\fR is changed and the lockfile has not been updated, running Bundler commands will be blocked\. Defaults to \fBtrue\fR when \fB\-\-deployment\fR is used\.
 .
 .IP "\(bu" 4
+\fBgem\.github_username\fR (\fBBUNDLE_GEM__GITHUB_USERNAME\fR): Sets a GitHub username or organization to be used in \fBREADME\fR file when you create a new gem via \fBbundle gem\fR command\. It can be overriden by passing an explicit \fB\-\-github\-username\fR flag to \fBbundle gem\fR\.
+.
+.IP "\(bu" 4
 \fBgem\.push_key\fR (\fBBUNDLE_GEM__PUSH_KEY\fR): Sets the \fB\-\-key\fR parameter for \fBgem push\fR when using the \fBrake release\fR command with a private gemstash server\.
 .
 .IP "\(bu" 4
@@ -223,9 +226,6 @@ The following is a list of all configuration keys and their purpose\. You can le
 \fBno_prune\fR (\fBBUNDLE_NO_PRUNE\fR): Whether Bundler should leave outdated gems unpruned when caching\.
 .
 .IP "\(bu" 4
-\fBonly_update_to_newer_versions\fR (\fBBUNDLE_ONLY_UPDATE_TO_NEWER_VERSIONS\fR): During \fBbundle update\fR, only resolve to newer versions of the gems in the lockfile\.
-.
-.IP "\(bu" 4
 \fBpath\fR (\fBBUNDLE_PATH\fR): The location on disk where all gems in your bundle will be located regardless of \fB$GEM_HOME\fR or \fB$GEM_PATH\fR values\. Bundle gems not found in this location will be installed by \fBbundle install\fR\. Defaults to \fBGem\.dir\fR\. When \-\-deployment is used, defaults to vendor/bundle\.
 .
 .IP "\(bu" 4
diff --git a/lib/bundler/man/bundle-config.1.ronn b/lib/bundler/man/bundle-config.1.ronn
index dc99c69412..ba4bd5ff23 100644
--- a/lib/bundler/man/bundle-config.1.ronn
+++ b/lib/bundler/man/bundle-config.1.ronn
@@ -194,6 +194,10 @@ learn more about their operation in [bundle install(1)](bundle-install.1.html).
    Disallow changes to the `Gemfile`. When the `Gemfile` is changed and the
    lockfile has not been updated, running Bundler commands will be blocked.
    Defaults to `true` when `--deployment` is used.
+* `gem.github_username` (`BUNDLE_GEM__GITHUB_USERNAME`):
+   Sets a GitHub username or organization to be used in `README` file when you
+   create a new gem via `bundle gem` command. It can be overriden by passing an
+   explicit `--github-username` flag to `bundle gem`.
 * `gem.push_key` (`BUNDLE_GEM__PUSH_KEY`):
    Sets the `--key` parameter for `gem push` when using the `rake release`
    command with a private gemstash server.
@@ -218,9 +222,6 @@ learn more about their operation in [bundle install(1)](bundle-install.1.html).
    Whether `bundle package` should skip installing gems.
 * `no_prune` (`BUNDLE_NO_PRUNE`):
    Whether Bundler should leave outdated gems unpruned when caching.
-* `only_update_to_newer_versions` (`BUNDLE_ONLY_UPDATE_TO_NEWER_VERSIONS`):
-   During `bundle update`, only resolve to newer versions of the gems in the
-   lockfile.
 * `path` (`BUNDLE_PATH`):
    The location on disk where all gems in your bundle will be located regardless
    of `$GEM_HOME` or `$GEM_PATH` values. Bundle gems not found in this location
diff --git a/lib/bundler/man/bundle-doctor.1 b/lib/bundler/man/bundle-doctor.1
index 2923517608..8e4c47c683 100644
--- a/lib/bundler/man/bundle-doctor.1
+++ b/lib/bundler/man/bundle-doctor.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-DOCTOR" "1" "January 2021" "" ""
+.TH "BUNDLE\-DOCTOR" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-doctor\fR \- Checks the bundle for common problems
diff --git a/lib/bundler/man/bundle-exec.1 b/lib/bundler/man/bundle-exec.1
index aa0c509278..863b76e4b7 100644
--- a/lib/bundler/man/bundle-exec.1
+++ b/lib/bundler/man/bundle-exec.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-EXEC" "1" "January 2021" "" ""
+.TH "BUNDLE\-EXEC" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-exec\fR \- Execute a command in the context of the bundle
diff --git a/lib/bundler/man/bundle-gem.1 b/lib/bundler/man/bundle-gem.1
index c1abf90f5c..e71ccb4832 100644
--- a/lib/bundler/man/bundle-gem.1
+++ b/lib/bundler/man/bundle-gem.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-GEM" "1" "January 2021" "" ""
+.TH "BUNDLE\-GEM" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-gem\fR \- Generate a project skeleton for creating a rubygem
diff --git a/lib/bundler/man/bundle-info.1 b/lib/bundler/man/bundle-info.1
index c715af4063..168d021112 100644
--- a/lib/bundler/man/bundle-info.1
+++ b/lib/bundler/man/bundle-info.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-INFO" "1" "January 2021" "" ""
+.TH "BUNDLE\-INFO" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-info\fR \- Show information for the given gem in your bundle
diff --git a/lib/bundler/man/bundle-init.1 b/lib/bundler/man/bundle-init.1
index 6c8f441bdd..5d3e61d05b 100644
--- a/lib/bundler/man/bundle-init.1
+++ b/lib/bundler/man/bundle-init.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-INIT" "1" "January 2021" "" ""
+.TH "BUNDLE\-INIT" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-init\fR \- Generates a Gemfile into the current working directory
diff --git a/lib/bundler/man/bundle-inject.1 b/lib/bundler/man/bundle-inject.1
index 2342b44716..37acabfa9a 100644
--- a/lib/bundler/man/bundle-inject.1
+++ b/lib/bundler/man/bundle-inject.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-INJECT" "1" "January 2021" "" ""
+.TH "BUNDLE\-INJECT" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-inject\fR \- Add named gem(s) with version requirements to Gemfile
diff --git a/lib/bundler/man/bundle-install.1 b/lib/bundler/man/bundle-install.1
index c223185b6f..2dcb4d3ac6 100644
--- a/lib/bundler/man/bundle-install.1
+++ b/lib/bundler/man/bundle-install.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-INSTALL" "1" "January 2021" "" ""
+.TH "BUNDLE\-INSTALL" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-install\fR \- Install the dependencies specified in your Gemfile
diff --git a/lib/bundler/man/bundle-list.1 b/lib/bundler/man/bundle-list.1
index 929b0f79f8..7c93b89dc3 100644
--- a/lib/bundler/man/bundle-list.1
+++ b/lib/bundler/man/bundle-list.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-LIST" "1" "January 2021" "" ""
+.TH "BUNDLE\-LIST" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-list\fR \- List all the gems in the bundle
diff --git a/lib/bundler/man/bundle-lock.1 b/lib/bundler/man/bundle-lock.1
index bcf588a3cf..a4dfda9c86 100644
--- a/lib/bundler/man/bundle-lock.1
+++ b/lib/bundler/man/bundle-lock.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-LOCK" "1" "January 2021" "" ""
+.TH "BUNDLE\-LOCK" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-lock\fR \- Creates / Updates a lockfile without installing
diff --git a/lib/bundler/man/bundle-open.1 b/lib/bundler/man/bundle-open.1
index 27308ff624..0511bc655b 100644
--- a/lib/bundler/man/bundle-open.1
+++ b/lib/bundler/man/bundle-open.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-OPEN" "1" "January 2021" "" ""
+.TH "BUNDLE\-OPEN" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-open\fR \- Opens the source directory for a gem in your bundle
diff --git a/lib/bundler/man/bundle-outdated.1 b/lib/bundler/man/bundle-outdated.1
index 40b23568d5..268b4b157c 100644
--- a/lib/bundler/man/bundle-outdated.1
+++ b/lib/bundler/man/bundle-outdated.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-OUTDATED" "1" "January 2021" "" ""
+.TH "BUNDLE\-OUTDATED" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-outdated\fR \- List installed gems with newer versions available
diff --git a/lib/bundler/man/bundle-platform.1 b/lib/bundler/man/bundle-platform.1
index d0ec5c643c..77638b2b4b 100644
--- a/lib/bundler/man/bundle-platform.1
+++ b/lib/bundler/man/bundle-platform.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-PLATFORM" "1" "January 2021" "" ""
+.TH "BUNDLE\-PLATFORM" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-platform\fR \- Displays platform compatibility information
diff --git a/lib/bundler/man/bundle-pristine.1 b/lib/bundler/man/bundle-pristine.1
index 9fd42d04a4..0fcf9fdb39 100644
--- a/lib/bundler/man/bundle-pristine.1
+++ b/lib/bundler/man/bundle-pristine.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-PRISTINE" "1" "January 2021" "" ""
+.TH "BUNDLE\-PRISTINE" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-pristine\fR \- Restores installed gems to their pristine condition
diff --git a/lib/bundler/man/bundle-remove.1 b/lib/bundler/man/bundle-remove.1
index 366e5f4be2..ca366b81a9 100644
--- a/lib/bundler/man/bundle-remove.1
+++ b/lib/bundler/man/bundle-remove.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-REMOVE" "1" "January 2021" "" ""
+.TH "BUNDLE\-REMOVE" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-remove\fR \- Removes gems from the Gemfile
diff --git a/lib/bundler/man/bundle-show.1 b/lib/bundler/man/bundle-show.1
index e2de241438..e403ae980f 100644
--- a/lib/bundler/man/bundle-show.1
+++ b/lib/bundler/man/bundle-show.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-SHOW" "1" "January 2021" "" ""
+.TH "BUNDLE\-SHOW" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-show\fR \- Shows all the gems in your bundle, or the path to a gem
diff --git a/lib/bundler/man/bundle-update.1 b/lib/bundler/man/bundle-update.1
index a78633bbf8..5546b51792 100644
--- a/lib/bundler/man/bundle-update.1
+++ b/lib/bundler/man/bundle-update.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-UPDATE" "1" "January 2021" "" ""
+.TH "BUNDLE\-UPDATE" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-update\fR \- Update your gems to the latest available versions
diff --git a/lib/bundler/man/bundle-viz.1 b/lib/bundler/man/bundle-viz.1
index fead09e6ad..645c45b607 100644
--- a/lib/bundler/man/bundle-viz.1
+++ b/lib/bundler/man/bundle-viz.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE\-VIZ" "1" "January 2021" "" ""
+.TH "BUNDLE\-VIZ" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\-viz\fR \- Generates a visual dependency graph for your Gemfile
diff --git a/lib/bundler/man/bundle.1 b/lib/bundler/man/bundle.1
index 50aa6e17c7..5c1bc96572 100644
--- a/lib/bundler/man/bundle.1
+++ b/lib/bundler/man/bundle.1
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "BUNDLE" "1" "January 2021" "" ""
+.TH "BUNDLE" "1" "April 2021" "" ""
 .
 .SH "NAME"
 \fBbundle\fR \- Ruby Dependency Management
diff --git a/lib/bundler/man/gemfile.5 b/lib/bundler/man/gemfile.5
index 3942806f75..480d38f39c 100644
--- a/lib/bundler/man/gemfile.5
+++ b/lib/bundler/man/gemfile.5
@@ -1,7 +1,7 @@
 .\" generated with Ronn/v0.7.3
 .\" http://github.com/rtomayko/ronn/tree/0.7.3
 .
-.TH "GEMFILE" "5" "January 2021" "" ""
+.TH "GEMFILE" "5" "April 2021" "" ""
 .
 .SH "NAME"
 \fBGemfile\fR \- A format for describing gem dependencies for Ruby programs
diff --git a/lib/bundler/settings.rb b/lib/bundler/settings.rb
index 749e4eb60e..2c0edd0c68 100644
--- a/lib/bundler/settings.rb
+++ b/lib/bundler/settings.rb
@@ -33,7 +33,6 @@ module Bundler
       init_gems_rb
       no_install
       no_prune
-      only_update_to_newer_versions
       path_relative_to_cwd
       path.system
       plugins
diff --git a/lib/bundler/templates/newgem/github/workflows/main.yml.tt b/lib/bundler/templates/newgem/github/workflows/main.yml.tt
index 807c8dd79a..654978033f 100644
--- a/lib/bundler/templates/newgem/github/workflows/main.yml.tt
+++ b/lib/bundler/templates/newgem/github/workflows/main.yml.tt
@@ -11,8 +11,6 @@ jobs:
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: <%= RUBY_VERSION %>
+        bundler-cache: true
     - name: Run the default task
-      run: |
-        gem install bundler -v <%= Bundler::VERSION %>
-        bundle install
-        bundle exec rake
+      run: bundle exec rake
diff --git a/lib/bundler/vendor/tmpdir/lib/tmpdir.rb b/lib/bundler/vendor/tmpdir/lib/tmpdir.rb
index a00496687c..70d43e0c6b 100644
--- a/lib/bundler/vendor/tmpdir/lib/tmpdir.rb
+++ b/lib/bundler/vendor/tmpdir/lib/tmpdir.rb
@@ -115,7 +115,7 @@ class Bundler::Dir < Dir
       Bundler::Dir.tmpdir
     end
 
-    UNUSABLE_CHARS = [File::SEPARATOR, File::ALT_SEPARATOR, File::PATH_SEPARATOR, ":"].uniq.join("").freeze
+    UNUSABLE_CHARS = "^,-.0-9A-Z_a-z~"
 
     class << (RANDOM = Random.new)
       MAX = 36**6 # < 0x100000000
diff --git a/lib/bundler/version.rb b/lib/bundler/version.rb
index 5b6473c465..1f5014bc1f 100644
--- a/lib/bundler/version.rb
+++ b/lib/bundler/version.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: false
 
 module Bundler
-  VERSION = "2.2.15".freeze
+  VERSION = "2.2.16".freeze
 
   def self.bundler_major_version
     @bundler_major_version ||= VERSION.split(".").first.to_i
diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index 61a2d465a2..57574474ea 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -8,7 +8,7 @@
 require 'rbconfig'
 
 module Gem
-  VERSION = "3.2.15".freeze
+  VERSION = "3.2.16".freeze
 end
 
 # Must be first since it unloads the prelude from 1.9.2
diff --git a/lib/rubygems/installer.rb b/lib/rubygems/installer.rb
index 3ec6d743a2..7af51056b7 100644
--- a/lib/rubygems/installer.rb
+++ b/lib/rubygems/installer.rb
@@ -484,8 +484,11 @@ class Gem::Installer
       bin_path = File.join gem_dir, spec.bindir, filename
 
       unless File.exist? bin_path
-        # TODO change this to a more useful warning
-        warn "`#{bin_path}` does not exist, maybe `gem pristine #{spec.name}` will fix it?"
+        if File.symlink? bin_path
+          alert_warning "`#{bin_path}` is dangling symlink pointing to `#{File.readlink bin_path}`"
+        else
+          alert_warning "`#{bin_path}` does not exist, maybe `gem pristine #{spec.name}` will fix it?"
+        end
         next
       end
 
diff --git a/lib/rubygems/package.rb b/lib/rubygems/package.rb
index 0587cd212b..a4ae3e9ea5 100644
--- a/lib/rubygems/package.rb
+++ b/lib/rubygems/package.rb
@@ -252,14 +252,7 @@ class Gem::Package
       stat = File.lstat file
 
       if stat.symlink?
-        target_path = File.readlink(file)
-
-        unless target_path.start_with? '.'
-          relative_dir = File.dirname(file).sub("#{Dir.pwd}/", '')
-          target_path = File.join(relative_dir, target_path)
-        end
-
-        tar.add_symlink file, target_path, stat.mode
+        tar.add_symlink file, File.readlink(file), stat.mode
       end
 
       next unless stat.file?
diff --git a/spec/bundler/bundler/dep_proxy_spec.rb b/spec/bundler/bundler/dep_proxy_spec.rb
index 84243d2ee2..8d02a33725 100644
--- a/spec/bundler/bundler/dep_proxy_spec.rb
+++ b/spec/bundler/bundler/dep_proxy_spec.rb
@@ -22,7 +22,7 @@ RSpec.describe Bundler::DepProxy do
   end
 
   describe "frozen" do
-    if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("2.5.0")
+    if Gem.ruby_version >= Gem::Version.new("2.5.0")
       error = Object.const_get("FrozenError")
     else
       error = RuntimeError
diff --git a/spec/bundler/bundler/gem_helper_spec.rb b/spec/bundler/bundler/gem_helper_spec.rb
index d718615ad2..43c9329fdb 100644
--- a/spec/bundler/bundler/gem_helper_spec.rb
+++ b/spec/bundler/bundler/gem_helper_spec.rb
@@ -61,10 +61,16 @@ RSpec.describe Bundler::GemHelper do
       mock_confirm_message message
     end
 
+    def mock_checksum_message(name, version)
+      message = "#{name} #{version} checksum written to checksums/#{name}-#{version}.gem.sha512."
+      mock_confirm_message message
+    end
+
     subject! { Bundler::GemHelper.new(app_path) }
     let(:app_version) { "0.1.0" }
     let(:app_gem_dir) { app_path.join("pkg") }
     let(:app_gem_path) { app_gem_dir.join("#{app_name}-#{app_version}.gem") }
+    let(:app_sha_path) { app_path.join("checksums", "#{app_name}-#{app_version}.gem.sha512") }
     let(:app_gemspec_content) { File.read(app_gemspec_path) }
 
     before(:each) do
@@ -162,6 +168,37 @@ RSpec.describe Bundler::GemHelper do
       end
     end
 
+    describe "#build_checksum" do
+      context "when build was successful" do
+        it "creates .sha512 file" do
+          mock_build_message app_name, app_version
+          mock_checksum_message app_name, app_version
+          subject.build_checksum
+          expect(app_sha_path).to exist
+        end
+      end
+      context "when building in the current working directory" do
+        it "creates a .sha512 file" do
+          mock_build_message app_name, app_version
+          mock_checksum_message app_name, app_version
+          Dir.chdir app_path do
+            Bundler::GemHelper.new.build_checksum
+          end
+          expect(app_sha_path).to exist
+        end
+      end
+      context "when building in a location relative to the current working directory" do
+        it "creates a .sha512 file" do
+          mock_build_message app_name, app_version
+          mock_checksum_message app_name, app_version
+          Dir.chdir File.dirname(app_path) do
+            Bundler::GemHelper.new(File.basename(app_path)).build_checksum
+          end
+          expect(app_sha_path).to exist
+        end
+      end
+    end
+
     describe "#install_gem" do
       context "when installation was successful" do
         it "gem is installed" do
diff --git a/spec/bundler/commands/info_spec.rb b/spec/bundler/commands/info_spec.rb
index 7702959306..daed4587d5 100644
--- a/spec/bundler/commands/info_spec.rb
+++ b/spec/bundler/commands/info_spec.rb
@@ -182,4 +182,18 @@ RSpec.describe "bundle info" do
       expect(err).to include("Could not find gem '#{invalid_regexp}'.")
     end
   end
+
+  context "with without configured" do
+    it "does not find the gem, but gives a helpful error" do
+      bundle "config without test"
+
+      install_gemfile <<-G
+        source "#{file_uri_for(gem_repo1)}"
+        gem "rails", group: :test
+      G
+
+      bundle "info rails", :raise_on_error => false
+      expect(err).to include("Could not find gem 'rails', because it's in the group 'test', configured to be ignored.")
+    end
+  end
 end
diff --git a/spec/bundler/commands/newgem_spec.rb b/spec/bundler/commands/newgem_spec.rb
index 297d380059..ac452a737a 100644
--- a/spec/bundler/commands/newgem_spec.rb
+++ b/spec/bundler/commands/newgem_spec.rb
@@ -12,12 +12,7 @@ RSpec.describe "bundle gem" do
 
   def bundle_exec_rubocop
     prepare_gemspec(bundled_app(gem_name, "#{gem_name}.gemspec"))
-    rubocop_version = RUBY_VERSION > "2.4" ? "1.7.0" : "0.81.0"
-    gems = ["minitest", "rake", "rake-compiler", "rspec", "rubocop -v #{rubocop_version}", "test-unit"]
-    gems.unshift "parallel -v 1.19.2" if RUBY_VERSION < "2.5"
-    gems += ["rubocop-ast -v 1.4.0"] if rubocop_version == "1.7.0"
-    path = Bundler.feature_flag.default_install_uses_path? ? local_gem_path(:base => bundled_app(gem_name)) : system_gem_path
-    realworld_system_gems gems, :path => path
+    bundle "config set path #{rubocop_gems}", :dir => bundled_app(gem_name)
     bundle "exec rubocop --debug --config .rubocop.yml", :dir => bundled_app(gem_name)
   end
 
@@ -351,6 +346,55 @@ RSpec.describe "bundle gem" do
     end
   end
 
+  shared_examples_for "--github-username option" do |github_username|
+    before do
+      bundle "gem #{gem_name} --github-username=#{github_username}"
+    end
+
+    it "generates a gem skeleton" do
+      gem_skeleton_assertions
+    end
+
+    it "contribute URL set to given github username" do
+      expect(bundled_app("#{gem_name}/README.md").read).not_to include("[USERNAME]")
+      expect(bundled_app("#{gem_name}/README.md").read).to include("github.com/#{github_username}")
+    end
+  end
+
+  shared_examples_for "github_username configuration" do
+    context "with github_username setting set to some value" do
+      before do
+        global_config "BUNDLE_GEM__GITHUB_USERNAME" => "different_username"
+        bundle "gem #{gem_name}"
+      end
+
+      it "generates a gem skeleton" do
+        gem_skeleton_assertions
+      end
+
+      it "contribute URL set to bundle config setting" do
+        expect(bundled_app("#{gem_name}/README.md").read).not_to include("[USERNAME]")
+        expect(bundled_app("#{gem_name}/README.md").read).to include("github.com/different_username")
+      end
+    end
+
+    context "with github_username setting set to false" do
+      before do
+        global_config "BUNDLE_GEM__GITHUB_USERNAME" => "false"
+        bundle "gem #{gem_name}"
+      end
+
+      it "generates a gem skeleton" do
+        gem_skeleton_assertions
+      end
+
+      it "contribute URL set to [USERNAME]" do
+        expect(bundled_app("#{gem_name}/README.md").read).to include("[USERNAME]")
+        expect(bundled_app("#{gem_name}/README.md").read).not_to include("github.com/bundleuser")
+      end
+    end
+  end
+
   shared_examples_for "generating a gem" do
     it "generates a gem skeleton" do
       bundle "gem #{gem_name}"
@@ -920,6 +964,57 @@ RSpec.describe "bundle gem" do
     end
   end
 
+  context "testing --github-username option against git and bundle config settings", :readline do
+    context "without git config set" do
+      before do
+        sys_exec("git config --global --unset github.user")
+      end
+      context "with github-username option in bundle config settings set to some value" do
+        before do
+          global_config "BUNDLE_GEM__GITHUB_USERNAME" => "different_username"
+        end
+        it_behaves_like "--github-username option", "gh_user"
+      end
+
+      context "with github-username option in bundle config settings set to false" do
+        before do
+          global_config "BUNDLE_GEM__GITHUB_USERNAME" => "false"
+        end
+        it_behaves_like "--github-username option", "gh_user"
+      end
+    end
+
+    context "with git config set" do
+      context "with github-username option in bundle config settings set to some value" do
+        before do
+          global_config "BUNDLE_GEM__GITHUB_USERNAME" => "different_username"
+        end
+        it_behaves_like "--github-username option", "gh_user"
+      end
+
+      context "with github-username option in bundle config settings set to false" do
+        before do
+          global_config "BUNDLE_GEM__GITHUB_USERNAME" => "false"
+        end
+        it_behaves_like "--github-username option", "gh_user"
+      end
+    end
+  end
+
+  context "testing github_username bundle config against git config settings", :readline do
+    context "without git config set" do
+      before do
+        sys_exec("git config --global --unset github.user")
+      end
+
+      it_behaves_like "github_username configuration"
+    end
+
+    context "with git config set" do
+      it_behaves_like "github_username configuration"
+    end
+  end
+
   context "gem naming with underscore", :readline do
     let(:gem_name) { "test_gem" }
 
diff --git a/spec/bundler/commands/outdated_spec.rb b/spec/bundler/commands/outdated_spec.rb
index 0ee8bd425a..7c4005824c 100644
--- a/spec/bundler/commands/outdated_spec.rb
+++ b/spec/bundler/commands/outdated_spec.rb
@@ -929,4 +929,54 @@ RSpec.describe "bundle outdated" do
       expect(out).to end_with(expected_output)
     end
   end
+
+  describe "with a multiplatform lockfile" do
+    before do
+      build_repo4 do
+        build_gem "nokogiri", "1.11.1"
+        build_gem "nokogiri", "1.11.1" do |s|
+          s.platform = Bundler.local_platform
+        end
+
+        build_gem "nokogiri", "1.11.2"
+        build_gem "nokogiri", "1.11.2" do |s|
+          s.platform = Bundler.local_platform
+        end
+      end
+
+      lockfile <<~L
+        GEM
+          remote: #{file_uri_for(gem_repo4)}/
+          specs:
+            nokogiri (1.11.1)
+            nokogiri (1.11.1-#{Bundler.local_platform})
+
+        PLATFORMS
+          ruby
+          #{Bundler.local_platform}
+
+        DEPENDENCIES
+          nokogiri
+
+        BUNDLED WITH
+           #{Bundler::VERSION}
+      L
+
+      gemfile <<-G
+        source "#{file_uri_for(gem_repo4)}"
+        gem "nokogiri"
+      G
+    end
+
+    it "reports a single entry per gem" do
+      bundle "outdated", :raise_on_error => false
+
+      expected_output = <<~TABLE.strip
+        Gem       Current  Latest  Requested  Groups
+        nokogiri  1.11.1   1.11.2  >= 0       default
+      TABLE
+
+      expect(out).to end_with(expected_output)
+    end
+  end
 end
diff --git a/spec/bundler/commands/post_bundle_message_spec.rb b/spec/bundler/commands/post_bundle_message_spec.rb
index 3f81808980..3092f9a9b7 100644
--- a/spec/bundler/commands/post_bundle_message_spec.rb
+++ b/spec/bundler/commands/post_bundle_message_spec.rb
@@ -32,21 +32,21 @@ RSpec.describe "post bundle message" do
       bundle "config --local without emo"
       bundle :install
       expect(out).to include(bundle_show_message)
-      expect(out).to include("Gems in the group emo were not installed")
+      expect(out).to include("Gems in the group 'emo' were not installed")
       expect(out).to include(bundle_complete_message)
       expect(out).to include(installed_gems_stats)
 
       bundle "config --local without emo test"
       bundle :install
       expect(out).to include(bundle_show_message)
-      expect(out).to include("Gems in the groups emo and test were not installed")
+      expect(out).to include("Gems in the groups 'emo' and 'test' were not installed")
       expect(out).to include(bundle_complete_message)
       expect(out).to include("4 Gemfile dependencies, 3 gems now installed.")
 
       bundle "config --local without emo obama test"
       bundle :install
       expect(out).to include(bundle_show_message)
-      expect(out).to include("Gems in the groups emo, obama and test were not installed")
+      expect(out).to include("Gems in the groups 'emo', 'obama' and 'test' were not installed")
       expect(out).to include(bundle_complete_message)
       expect(out).to include("4 Gemfile dependencies, 2 gems now installed.")
     end
@@ -65,21 +65,21 @@ RSpec.describe "post bundle message" do
         bundle "config --local without emo"
         bundle :install
         expect(out).to include(bundle_show_path_message)
-        expect(out).to include("Gems in the group emo were not installed")
+        expect(out).to include("Gems in the group 'emo' were not installed")
         expect(out).to include(bundle_complete_message)
 
         bundle "config --local path vendor"
         bundle "config --local without emo test"
         bundle :install
         expect(out).to include(bundle_show_path_message)
-        expect(out).to include("Gems in the groups emo and test were not installed")
+        expect(out).to include("Gems in the groups 'emo' and 'test' were not installed")
         expect(out).to include(bundle_complete_message)
 
         bundle "config --local path vendor"
         bundle "config --local without emo obama test"
         bundle :install
         expect(out).to include(bundle_show_path_message)
-        expect(out).to include("Gems in the groups emo, obama and test were not installed")
+        expect(out).to include("Gems in the groups 'emo', 'obama' and 'test' were not installed")
         expect(out).to include(bundle_complete_message)
       end
     end
@@ -156,7 +156,7 @@ The source does not contain any versions of 'not-a-gem'
       bundle "install --without emo"
       bundle :install
       expect(out).to include(bundle_show_message)
-      expect(out).to include("Gems in the group emo were not installed")
+      expect(out).to include("Gems in the group 'emo' were not installed")
       expect(out).to include(bundle_complete_message)
       expect(out).to include(installed_gems_stats)
     end
@@ -165,7 +165,7 @@ The source does not contain any versions of 'not-a-gem'
       bundle "install --without emo test"
       bundle :install
       expect(out).to include(bundle_show_message)
-      expect(out).to include("Gems in the groups emo and test were not installed")
+      expect(out).to include("Gems in the groups 'emo' and 'test' were not installed")
       expect(out).to include(bundle_complete_message)
     end
 
@@ -173,7 +173,7 @@ The source does not contain any versions of 'not-a-gem'
       bundle "install --without emo obama test"
       bundle :install
       expect(out).to include(bundle_show_message)
-      expect(out).to include("Gems in the groups emo, obama and test were not installed")
+      expect(out).to include("Gems in the groups 'emo', 'obama' and 'test' were not installed")
       expect(out).to include(bundle_complete_message)
     end
   end
@@ -187,19 +187,19 @@ The source does not contain any versions of 'not-a-gem'
       bundle "config --local without emo"
       bundle :install
       bundle :update, :all => true
-      expect(out).to include("Gems in the group emo were not updated")
+      expect(out).to include("Gems in the group 'emo' were not updated")
       expect(out).to include(bundle_updated_message)
 
       bundle "config --local without emo test"
       bundle :install
       bundle :update, :all => true
-      expect(out).to include("Gems in the groups emo and test were not updated")
+      expect(out).to include("Gems in the groups 'emo' and 'test' were not updated")
       expect(out).to include(bundle_updated_message)
 
       bundle "config --local without emo obama test"
       bundle :install
       bundle :update, :all => true
-      expect(out).to include("Gems in the groups emo, obama and test were not updated")
+      expect(out).to include("Gems in the groups 'emo', 'obama' and 'test' were not updated")
       expect(out).to include(bundle_updated_message)
     end
   end
diff --git a/spec/bundler/commands/update_spec.rb b/spec/bundler/commands/update_spec.rb
index 521c175711..0f17d931a3 100644
--- a/spec/bundler/commands/update_spec.rb
+++ b/spec/bundler/commands/update_spec.rb
@@ -148,72 +148,66 @@ RSpec.describe "bundle update" do
   end
 
   describe "when a possible resolve requires an older version of a locked gem" do
-    context "and only_update_to_newer_versions is set" do
-      before do
-        bundle "config set only_update_to_newer_versions true"
+    it "does not go to an older version" do
+      build_repo4 do
+        build_gem "tilt", "2.0.8"
+        build_gem "slim", "3.0.9" do |s|
+          s.add_dependency "tilt", [">= 1.3.3", "< 2.1"]
+        end
+        build_gem "slim_lint", "0.16.1" do |s|
+          s.add_dependency "slim", [">= 3.0", "< 5.0"]
+        end
+        build_gem "slim-rails", "0.2.1" do |s|
+          s.add_dependency "slim", ">= 0.9.2"
+        end
+        build_gem "slim-rails", "3.1.3" do |s|
+          s.add_dependency "slim", "~> 3.0"
+        end
       end
 
-      it "does not go to an older version" do
-        build_repo4 do
-          build_gem "tilt", "2.0.8"
-          build_gem "slim", "3.0.9" do |s|
-            s.add_dependency "tilt", [">= 1.3.3", "< 2.1"]
-          end
-          build_gem "slim_lint", "0.16.1" do |s|
-            s.add_dependency "slim", [">= 3.0", "< 5.0"]
-          end
-          build_gem "slim-rails", "0.2.1" do |s|
-            s.add_dependency "slim", ">= 0.9.2"
-          end
-          build_gem "slim-rails", "3.1.3" do |s|
-            s.add_dependency "slim", "~> 3.0"
-          end
+      install_gemfile <<-G
+        source "#{file_uri_for(gem_repo4)}"
+        gem "slim-rails"
+        gem "slim_lint"
+      G
+
+      expect(the_bundle).to include_gems("slim 3.0.9", "slim-rails 3.1.3", "slim_lint 0.16.1")
+
+      update_repo4 do
+        build_gem "slim", "4.0.0" do |s|
+          s.add_dependency "tilt", [">= 2.0.6", "< 2.1"]
         end
-
-        install_gemfile <<-G
-          source "#{file_uri_for(gem_repo4)}"
-          gem "slim-rails"
-          gem "slim_lint"
-        G
-
-        expect(the_bundle).to include_gems("slim 3.0.9", "slim-rails 3.1.3", "slim_lint 0.16.1")
-
-        update_repo4 do
-          build_gem "slim", "4.0.0" do |s|
-            s.add_dependency "tilt", [">= 2.0.6", "< 2.1"]
-          end
-        end
-
-        bundle "update", :all => true
-
-        expect(the_bundle).to include_gems("slim 3.0.9", "slim-rails 3.1.3", "slim_lint 0.16.1")
       end
 
-      it "should still downgrade if forced by the Gemfile" do
-        build_repo4 do
-          build_gem "a"
-          build_gem "b", "1.0"
-          build_gem "b", "2.0"
-        end
+      bundle "update", :all => true
 
-        install_gemfile <<-G
-          source "#{file_uri_for(gem_repo4)}"
-          gem "a"
-          gem "b"
-        G
+      expect(the_bundle).to include_gems("slim 3.0.9", "slim-rails 3.1.3", "slim_lint 0.16.1")
+    end
 
-        expect(the_bundle).to include_gems("a 1.0", "b 2.0")
-
-        gemfile <<-G
-          source "#{file_uri_for(gem_repo4)}"
-          gem "a"
-          gem "b", "1.0"
-        G
-
-        bundle "update b"
-
-        expect(the_bundle).to include_gems("a 1.0", "b 1.0")
+    it "should still downgrade if forced by the Gemfile" do
+      build_repo4 do
+        build_gem "a"
+        build_gem "b", "1.0"
+        build_gem "b", "2.0"
       end
+
+      install_gemfile <<-G
+        source "#{file_uri_for(gem_repo4)}"
+        gem "a"
+        gem "b"
+      G
+
+      expect(the_bundle).to include_gems("a 1.0", "b 2.0")
+
+      gemfile <<-G
+        source "#{file_uri_for(gem_repo4)}"
+        gem "a"
+        gem "b", "1.0"
+      G
+
+      bundle "update b"
+
+      expect(the_bundle).to include_gems("a 1.0", "b 1.0")
     end
   end
 
diff --git a/spec/bundler/install/gemfile/gemspec_spec.rb b/spec/bundler/install/gemfile/gemspec_spec.rb
index 4001df26da..b04db18f49 100644
--- a/spec/bundler/install/gemfile/gemspec_spec.rb
+++ b/spec/bundler/install/gemfile/gemspec_spec.rb
@@ -259,7 +259,7 @@ RSpec.describe "bundle install from an existing gemspec" do
     expect(out).to eq("WIN")
   end
 
-  it "works with only_update_to_newer_versions" do
+  it "handles downgrades" do
     build_lib "omg", "2.0", :path => lib_path("omg")
 
     install_gemfile <<-G
@@ -268,7 +268,7 @@ RSpec.describe "bundle install from an existing gemspec" do
 
     build_lib "omg", "1.0", :path => lib_path("omg")
 
-    bundle :install, :env => { "BUNDLE_BUNDLE_ONLY_UPDATE_TO_NEWER_VERSIONS" => "true" }
+    bundle :install
 
     expect(the_bundle).to include_gems "omg 1.0"
   end
diff --git a/spec/bundler/install/gemfile/path_spec.rb b/spec/bundler/install/gemfile/path_spec.rb
index e78217d369..5772c4edc6 100644
--- a/spec/bundler/install/gemfile/path_spec.rb
+++ b/spec/bundler/install/gemfile/path_spec.rb
@@ -173,7 +173,7 @@ RSpec.describe "bundle install with explicit source paths" do
     expect(the_bundle).to include_gems "foo 1.0"
   end
 
-  it "works with only_update_to_newer_versions" do
+  it "handles downgrades" do
     build_lib "omg", "2.0", :path => lib_path("omg")
 
     install_gemfile <<-G
@@ -182,7 +182,7 @@ RSpec.describe "bundle install with explicit source paths" do
 
     build_lib "omg", "1.0", :path => lib_path("omg")
 
-    bundle :install, :env => { "BUNDLE_BUNDLE_ONLY_UPDATE_TO_NEWER_VERSIONS" => "true" }
+    bundle :install
 
     expect(the_bundle).to include_gems "omg 1.0"
   end
diff --git a/spec/bundler/install/gemfile/specific_platform_spec.rb b/spec/bundler/install/gemfile/specific_platform_spec.rb
index 9e30fc4fd4..a5b78443b9 100644
--- a/spec/bundler/install/gemfile/specific_platform_spec.rb
+++ b/spec/bundler/install/gemfile/specific_platform_spec.rb
@@ -104,6 +104,50 @@ RSpec.describe "bundle install with specific platforms" do
       L
     end
 
+    it "doesn't discard previously installed platform specific gem and fall back to ruby on subsequent bundles" do
+      build_repo2 do
+        build_gem("libv8", "8.4.255.0")
+        build_gem("libv8", "8.4.255.0") {|s| s.platform = "universal-darwin" }
+
+        build_gem("mini_racer", "1.0.0") do |s|
+          s.add_runtime_dependency "libv8"
+        end
+      end
+
+      system_gems "bundler-2.1.4"
+
+      # Consistent location to install and look for gems
+      bundle "config set --local path vendor/bundle", :env => { "BUNDLER_VERSION" => "2.1.4" }
+
+      gemfile <<-G
+        source "https://localgemserver.test"
+        gem "libv8"
+      G
+
+      # simulate lockfile created with old bundler, which only locks for ruby platform
+      lockfile <<-L
+        GEM
+          remote: https://localgemserver.test/
+          specs:
+            libv8 (8.4.255.0)
+
+        PLATFORMS
+          ruby
+
+        DEPENDENCIES
+          libv8
+
+        BUNDLED WITH
+           2.1.4
+      L
+
+      bundle "install --verbose", :artifice => :compact_index, :env => { "BUNDLER_VERSION" => "2.1.4", "BUNDLER_SPEC_GEM_REPO" => gem_repo2.to_s }
+      expect(out).to include("Installing libv8 8.4.255.0 (universal-darwin)")
+
+      bundle "add mini_racer --verbose", :artifice => :compact_index, :env => { "BUNDLER_SPEC_GEM_REPO" => gem_repo2.to_s }
+      expect(out).to include("Using libv8 8.4.255.0 (universal-darwin)")
+    end
+
     it "caches the universal-darwin gem when --all-platforms is passed and properly picks it up on further bundler invocations" do
       setup_multiplatform_gem
       gemfile(google_protobuf)
diff --git a/spec/bundler/runtime/setup_spec.rb b/spec/bundler/runtime/setup_spec.rb
index 7af1cd9801..46663bc76f 100644
--- a/spec/bundler/runtime/setup_spec.rb
+++ b/spec/bundler/runtime/setup_spec.rb
@@ -1244,16 +1244,16 @@ end
 
     describe "default gem activation" do
       let(:exemptions) do
-        exempts = if Gem::Version.new(Gem::VERSION) >= Gem::Version.new("2.7")
+        exempts = if Gem.rubygems_version >= Gem::Version.new("2.7")
           %w[did_you_mean]
         else
           %w[io-console openssl]
         end << "bundler"
-        exempts << "fiddle" if Gem.win_platform? && Gem::Version.new(Gem::VERSION) >= Gem::Version.new("2.7")
-        exempts << "uri" if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("2.7")
-        exempts << "pathname" if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("3.0")
-        exempts << "set" unless Gem::Version.new(Gem::VERSION) >= Gem::Version.new("3.2.6")
-        exempts << "tsort" if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new("3.0")
+        exempts << "fiddle" if Gem.win_platform? && Gem.rubygems_version >= Gem::Version.new("2.7")
+        exempts << "uri" if Gem.ruby_version >= Gem::Version.new("2.7")
+        exempts << "pathname" if Gem.ruby_version >= Gem::Version.new("3.0")
+        exempts << "set" unless Gem.rubygems_version >= Gem::Version.new("3.2.6")
+        exempts << "tsort" if Gem.ruby_version >= Gem::Version.new("3.0")
         exempts
       end
 
diff --git a/spec/bundler/spec_helper.rb b/spec/bundler/spec_helper.rb
index 6587ce5d55..d09ccb6e90 100644
--- a/spec/bundler/spec_helper.rb
+++ b/spec/bundler/spec_helper.rb
@@ -65,16 +65,9 @@ RSpec.configure do |config|
     mocks.allow_message_expectations_on_nil = false
   end
 
-  config.around :each do |example|
-    if ENV["RUBY"]
-      orig_ruby = Gem.ruby
-      Gem.ruby = ENV["RUBY"]
-    end
-    example.run
-    Gem.ruby = orig_ruby if ENV["RUBY"]
-  end
-
   config.before :suite do
+    Gem.ruby = ENV["RUBY"] if ENV["RUBY"]
+
     require_relative "support/rubygems_ext"
     Spec::Rubygems.test_setup
     ENV["BUNDLE_SPEC_RUN"] = "true"
diff --git a/spec/bundler/support/bundle.rb b/spec/bundler/support/bundle.rb
new file mode 100644
index 0000000000..bb21526d35
--- /dev/null
+++ b/spec/bundler/support/bundle.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+require "rubygems"
+require_relative "path"
+bundler_gemspec = Spec::Path.loaded_gemspec
+bundler_gemspec.instance_variable_set(:@full_gem_path, Spec::Path.source_root)
+bundler_gemspec.activate if bundler_gemspec.respond_to?(:activate)
+load File.expand_path("bundle", Spec::Path.bindir)
diff --git a/spec/bundler/support/hax.rb b/spec/bundler/support/hax.rb
index fc8e0ad55d..8fd35890ae 100644
--- a/spec/bundler/support/hax.rb
+++ b/spec/bundler/support/hax.rb
@@ -29,7 +29,7 @@ module Gem
   end
 
   # We only need this hack for rubygems versions without the BundlerVersionFinder
-  if Gem::Version.new(Gem::VERSION) < Gem::Version.new("2.7.0")
+  if Gem.rubygems_version < Gem::Version.new("2.7.0")
     @path_to_default_spec_map.delete_if do |_path, spec|
       spec.name == "bundler"
     end
diff --git a/spec/bundler/support/helpers.rb b/spec/bundler/support/helpers.rb
index 7e2e92a1ec..73dd508e54 100644
--- a/spec/bundler/support/helpers.rb
+++ b/spec/bundler/support/helpers.rb
@@ -10,7 +10,7 @@ module Spec
 
     def reset!
       Dir.glob("#{tmp}/{gems/*,*}", File::FNM_DOTMATCH).each do |dir|
-        next if %w[base base_system remote1 gems rubygems . ..].include?(File.basename(dir))
+        next if %w[base base_system remote1 rubocop gems rubygems . ..].include?(File.basename(dir))
         FileUtils.rm_rf(dir)
       end
       FileUtils.mkdir_p(home)
diff --git a/spec/bundler/support/path.rb b/spec/bundler/support/path.rb
index 56d3c71f3c..483c7da347 100644
--- a/spec/bundler/support/path.rb
+++ b/spec/bundler/support/path.rb
@@ -6,7 +6,7 @@ require "rbconfig"
 module Spec
   module Path
     def source_root
-      @source_root ||= Pathname.new(ruby_core? ? "../../../.." : "../../..").expand_path(__FILE__)
+      @source_root ||= Pathname.new(ruby_core? ? "../../.." : "../..").expand_path(__dir__)
     end
 
     def root
@@ -30,7 +30,11 @@ module Spec
     end
 
     def test_gemfile
-      @test_gemfile ||= source_root.join(ruby_core? ? "tool/bundler/test_gems.rb" : "test_gems.rb")
+      @test_gemfile ||= source_root.join("tool/bundler/test_gems.rb")
+    end
+
+    def rubocop_gemfile
+      @rubocop_gemfile ||= source_root.join(rubocop_gemfile_basename)
     end
 
     def dev_gemfile
@@ -119,7 +123,7 @@ module Spec
     end
 
     def vendored_gems(path = nil)
-      bundled_app(*["vendor/bundle", Gem.ruby_engine, RbConfig::CONFIG["ruby_version"], path].compact)
+      scoped_gem_path(bundled_app("vendor/bundle")).join(*[path].compact)
     end
 
     def cached_gem(path)
@@ -138,6 +142,10 @@ module Spec
       tmp.join("gems/base")
     end
 
+    def rubocop_gems
+      tmp.join("gems/rubocop")
+    end
+
     def file_uri_for(path)
       protocol = "file://"
       root = Gem.win_platform? ? "/" : ""
@@ -178,7 +186,11 @@ module Spec
     end
 
     def local_gem_path(*path, base: bundled_app)
-      base.join(*[".bundle", Gem.ruby_engine, RbConfig::CONFIG["ruby_version"], *path].compact)
+      scoped_gem_path(base.join(".bundle")).join(*path)
+    end
+
+    def scoped_gem_path(base)
+      base.join(Gem.ruby_engine, RbConfig::CONFIG["ruby_version"])
     end
 
     def lib_path(*args)
@@ -251,6 +263,10 @@ module Spec
       !git_root.join(".git").directory?
     end
 
+    def rubocop_gemfile_basename
+      source_root.join("tool/bundler/#{RUBY_VERSION.start_with?("2.3") ? "rubocop23_gems.rb" : "rubocop_gems.rb"}")
+    end
+
     extend self
   end
 end
diff --git a/spec/bundler/support/rubygems_ext.rb b/spec/bundler/support/rubygems_ext.rb
index d743a76391..c6202ebb1f 100644
--- a/spec/bundler/support/rubygems_ext.rb
+++ b/spec/bundler/support/rubygems_ext.rb
@@ -9,7 +9,7 @@ module Spec
     extend self
 
     def dev_setup
-      install_gems(dev_gemfile, dev_lockfile)
+      install_gems(dev_gemfile)
     end
 
     def gem_load(gem_name, bin_container)
@@ -39,18 +39,19 @@ module Spec
     end
 
     def install_parallel_test_deps
+      Gem.clear_paths
+
       require "parallel"
+      require "fileutils"
 
-      prev_env_test_number = ENV["TEST_ENV_NUMBER"]
+      install_test_deps
 
-      begin
-        Parallel.processor_count.times do |n|
-          ENV["TEST_ENV_NUMBER"] = (n + 1).to_s
+      (2..Parallel.processor_count).each do |n|
+        source = Path.source_root.join("tmp", "1")
+        destination = Path.source_root.join("tmp", n.to_s)
 
-          install_test_deps
-        end
-      ensure
-        ENV["TEST_ENV_NUMBER"] = prev_env_test_number
+        FileUtils.rm_rf destination
+        FileUtils.cp_r source, destination
       end
     end
 
@@ -66,25 +67,12 @@ module Spec
     def install_test_deps
       setup_test_paths
 
-      workaround_loaded_specs_issue
-
-      install_gems(test_gemfile, test_lockfile)
+      install_gems(test_gemfile)
+      install_gems(rubocop_gemfile, Path.rubocop_gems.to_s)
     end
 
     private
 
-    # Some rubygems versions include loaded specs when loading gemspec stubs
-    # from the file system. In this situation, that makes bundler incorrectly
-    # assume that `rake` is already installed at `tmp/` because it's installed
-    # globally, and makes it skip installing it to the proper location for our
-    # tests. To workaround, we remove `rake` from the loaded specs when running
-    # under those versions, so that `bundler` does the right thing.
-    def workaround_loaded_specs_issue
-      current_rubygems_version = Gem::Version.new(Gem::VERSION)
-
-      Gem.loaded_specs.delete("rake") if current_rubygems_version >= Gem::Version.new("3.0.0.beta2") && current_rubygems_version < Gem::Version.new("3.2.0")
-    end
-
     def gem_load_and_activate(gem_name, bin_container)
       gem_activate(gem_name)
       load Gem.bin_path(gem_name, bin_container)
@@ -98,14 +86,27 @@ module Spec
       gem gem_name, gem_requirement
     end
 
-    def install_gems(gemfile, lockfile)
+    def install_gems(gemfile, path = nil)
       old_gemfile = ENV["BUNDLE_GEMFILE"]
       ENV["BUNDLE_GEMFILE"] = gemfile.to_s
-      require "bundler"
-      definition = Bundler::Definition.build(gemfile, lockfile, nil)
-      definition.validate_runtime!
-      Bundler::Installer.install(Path.source_root, definition, :path => ENV["GEM_HOME"])
+
+      if path
+        old_path = ENV["BUNDLE_PATH"]
+        ENV["BUNDLE_PATH"] = path
+      else
+        old_path__system = ENV["BUNDLE_PATH__SYSTEM"]
+        ENV["BUNDLE_PATH__SYSTEM"] = "true"
+      end
+
+      output = `#{Gem.ruby} #{File.expand_path("support/bundle.rb", Path.spec_dir)} install`
+      raise "Error when installing gems in #{gemfile}: #{output}" unless $?.success?
     ensure
+      if path
+        ENV["BUNDLE_PATH"] = old_path
+      else
+        ENV["BUNDLE_PATH__SYSTEM"] = old_path__system
+      end
+
       ENV["BUNDLE_GEMFILE"] = old_gemfile
     end
 
@@ -113,8 +114,8 @@ module Spec
       Path.test_gemfile
     end
 
-    def test_lockfile
-      lockfile_for(test_gemfile)
+    def rubocop_gemfile
+      Path.rubocop_gemfile
     end
 
     def dev_gemfile
diff --git a/test/rubygems/packages/ascii_binder-0.1.10.1.gem b/test/rubygems/packages/ascii_binder-0.1.10.1.gem
new file mode 100644
index 0000000000..19c505395e
Binary files /dev/null and b/test/rubygems/packages/ascii_binder-0.1.10.1.gem differ
diff --git a/test/rubygems/test_gem_installer.rb b/test/rubygems/test_gem_installer.rb
index 5652d86331..058e3b3c20 100644
--- a/test/rubygems/test_gem_installer.rb
+++ b/test/rubygems/test_gem_installer.rb
@@ -735,6 +735,26 @@ gem 'other', version
     assert_match(/#{default_shebang}/, shebang_line)
   end
 
+  def test_generate_bin_with_dangling_symlink
+    gem_with_dangling_symlink = File.expand_path("packages/ascii_binder-0.1.10.1.gem", __dir__)
+
+    installer = Gem::Installer.at(
+      gem_with_dangling_symlink,
+      :install_dir => @gem_home,
+      :user_install => false,
+      :force => true
+    )
+
+    build_rake_in do
+      use_ui @ui do
+        installer.install
+      end
+    end
+
+    assert_match %r{bin/ascii_binder` is dangling symlink pointing to `bin/asciibinder`}, @ui.error
+    assert_empty @ui.output
+  end
+
   def test_generate_plugins
     installer = util_setup_installer do |spec|
       write_file File.join(@tempdir, 'lib', 'rubygems_plugin.rb') do |io|
diff --git a/test/rubygems/test_gem_package.rb b/test/rubygems/test_gem_package.rb
index fd28f9a2a5..eb10ea3437 100644
--- a/test/rubygems/test_gem_package.rb
+++ b/test/rubygems/test_gem_package.rb
@@ -218,7 +218,7 @@ class TestGemPackage < Gem::Package::TarTestCase
     end
 
     assert_equal %w[lib/code.rb], files
-    assert_equal [{'lib/code_sym.rb' => 'lib/code.rb'}, {'lib/code_sym2.rb' => '../lib/code.rb'}], symlinks
+    assert_equal [{'lib/code_sym.rb' => 'code.rb'}, {'lib/code_sym2.rb' => '../lib/code.rb'}], symlinks
   end
 
   def test_build