diff --git a/Library/Homebrew/brew.sh b/Library/Homebrew/brew.sh
index c7c42a6c4d..0a73e3b7b6 100644
--- a/Library/Homebrew/brew.sh
+++ b/Library/Homebrew/brew.sh
@@ -414,7 +414,8 @@ update-preinstall() {
   [[ -z "$HOMEBREW_AUTO_UPDATE_CHECKED" ]] || return
   [[ -z "$HOMEBREW_UPDATE_PREINSTALL" ]] || return
 
-  if [[ "$HOMEBREW_COMMAND" = "install" || "$HOMEBREW_COMMAND" = "upgrade" || "$HOMEBREW_COMMAND" = "tap" ||
+  if [[ "$HOMEBREW_COMMAND" = "install" || "$HOMEBREW_COMMAND" = "upgrade" ||
+        "$HOMEBREW_COMMAND" = "tap" && $HOMEBREW_ARG_COUNT -gt 1 ||
         "$HOMEBREW_CASK_COMMAND" = "install" || "$HOMEBREW_CASK_COMMAND" = "upgrade" ]]
   then
     export HOMEBREW_AUTO_UPDATING="1"
diff --git a/Library/Homebrew/cask/cmd/info.rb b/Library/Homebrew/cask/cmd/info.rb
index d81b5f44a6..ec160e6b4f 100644
--- a/Library/Homebrew/cask/cmd/info.rb
+++ b/Library/Homebrew/cask/cmd/info.rb
@@ -1,4 +1,5 @@
 require "json"
+require "cask/installer"
 
 module Cask
   class Cmd
@@ -51,12 +52,17 @@ module Cask
       end
 
       def self.installation_info(cask)
+        install_info = ""
         if cask.installed?
           cask.versions.each do |version|
             versioned_staged_path = cask.caskroom_path.join(version)
-            message = versioned_staged_path.exist? ? versioned_staged_path.abv : Formatter.error("does not exist")
-            versioned_staged_path.to_s.concat(" (").concat(message).concat(")")
+            install_info << versioned_staged_path.to_s
+              .concat(" (")
+              .concat(versioned_staged_path.exist? ? versioned_staged_path.abv : Formatter.error("does not exist"))
+                                      .concat(")")
+            install_info << "\n"
           end
+        return install_info.strip
         else
           "Not installed"
         end
diff --git a/Library/Homebrew/cli_parser.rb b/Library/Homebrew/cli_parser.rb
index f35328a574..d8440aed6e 100644
--- a/Library/Homebrew/cli_parser.rb
+++ b/Library/Homebrew/cli_parser.rb
@@ -135,6 +135,7 @@ module Homebrew
         check_constraint_violations
         Homebrew.args[:remaining] = remaining_args
         Homebrew.args.freeze
+        cmdline_args.freeze
         @parser
       end
 
diff --git a/Library/Homebrew/dev-cmd/irb.rb b/Library/Homebrew/dev-cmd/irb.rb
index 4e57bffd91..358feda611 100644
--- a/Library/Homebrew/dev-cmd/irb.rb
+++ b/Library/Homebrew/dev-cmd/irb.rb
@@ -31,7 +31,8 @@ module Homebrew
   end
 
   def irb
-    irb_args.parse
+    # work around IRB modifying ARGV.
+    irb_args.parse(ARGV.dup)
 
     if args.examples?
       puts "'v8'.f # => instance of the v8 formula"
diff --git a/Library/Homebrew/extend/ARGV.rb b/Library/Homebrew/extend/ARGV.rb
index ac931df1f5..857a856903 100644
--- a/Library/Homebrew/extend/ARGV.rb
+++ b/Library/Homebrew/extend/ARGV.rb
@@ -30,7 +30,8 @@ module HomebrewArgvExtension
   end
 
   def named
-    @named ||= self - options_only
+    # TODO: use @instance variable to ||= cache when moving to CLI::Parser
+    self - options_only
   end
 
   def options_only
@@ -43,7 +44,8 @@ module HomebrewArgvExtension
 
   def formulae
     require "formula"
-    @formulae ||= (downcased_unique_named - casks).map do |name|
+    # TODO: use @instance variable to ||= cache when moving to CLI::Parser
+    (downcased_unique_named - casks).map do |name|
       if name.include?("/") || File.exist?(name)
         Formulary.factory(name, spec)
       else
@@ -54,19 +56,22 @@ module HomebrewArgvExtension
 
   def resolved_formulae
     require "formula"
-    @resolved_formulae ||= (downcased_unique_named - casks).map do |name|
+    # TODO: use @instance variable to ||= cache when moving to CLI::Parser
+    (downcased_unique_named - casks).map do |name|
       Formulary.resolve(name, spec: spec(nil))
     end.uniq(&:name)
   end
 
   def casks
-    @casks ||= downcased_unique_named.grep HOMEBREW_CASK_TAP_CASK_REGEX
+    # TODO: use @instance variable to ||= cache when moving to CLI::Parser
+    downcased_unique_named.grep HOMEBREW_CASK_TAP_CASK_REGEX
   end
 
   def kegs
     require "keg"
     require "formula"
-    @kegs ||= downcased_unique_named.map do |name|
+    # TODO: use @instance variable to ||= cache when moving to CLI::Parser
+    downcased_unique_named.map do |name|
       raise UsageError if name.empty?
 
       rack = Formulary.to_rack(name.downcase)
@@ -109,7 +114,7 @@ module HomebrewArgvExtension
   end
 
   def include?(arg)
-    !(@n = index(arg)).nil?
+    !index(arg).nil?
   end
 
   def next
@@ -281,7 +286,8 @@ module HomebrewArgvExtension
 
   def downcased_unique_named
     # Only lowercase names, not paths, bottle filenames or URLs
-    @downcased_unique_named ||= named.map do |arg|
+    # TODO: use @instance variable to ||= cache when moving to CLI::Parser
+    named.map do |arg|
       if arg.include?("/") || arg.end_with?(".tar.gz") || File.exist?(arg)
         arg
       else
diff --git a/Library/Homebrew/missing_formula.rb b/Library/Homebrew/missing_formula.rb
index b066659512..22a0c4678f 100644
--- a/Library/Homebrew/missing_formula.rb
+++ b/Library/Homebrew/missing_formula.rb
@@ -1,8 +1,7 @@
 require "formulary"
 require "cask/cmd/abstract_command"
-require "cask/cmd"
+require "cask/cmd/info"
 require "cask/cask_loader"
-require "cask/installer"
 
 module Homebrew
   module MissingFormula
@@ -15,34 +14,35 @@ module Homebrew
       def blacklisted_reason(name)
         case name.downcase
         when "gem", /^rubygems?$/ then <<~EOS
-          Homebrew provides gem via: `brew install ruby`.
+          macOS provides gem as part of Ruby. To install a newer version:
+            brew install ruby
         EOS
         when "tex", "tex-live", "texlive", "latex" then <<~EOS
-          Installing TeX from source is weird and gross, requires a lot of patches,
-          and only builds 32-bit (and thus can't use Homebrew dependencies)
+          There are three versions of MacTeX.
 
-          We recommend using a MacTeX distribution: https://www.tug.org/mactex/
-
-          You can install it with Homebrew Cask:
+          Full installation:
             brew cask install mactex
+
+          Full installation without bundled applications:
+            brew cask install mactex-no-gui
+
+          Minimal installation:
+            brew cask install basictex
         EOS
         when "pip" then <<~EOS
-          pip is part of the python formula, and can be installed with:
+          pip is part of the python formula:
             brew install python
-          However you will then have two Pythons installed on your Mac,
-          so alternatively you can install pip via the instructions at:
-            #{Formatter.url("https://pip.readthedocs.io/en/stable/installing/")}
         EOS
         when "pil" then <<~EOS
-          Instead of PIL, consider `pip2 install pillow`.
+          Instead of PIL, consider pillow:
+            pip2 install pillow
         EOS
         when "macruby" then <<~EOS
-          MacRuby is not packaged and is on an indefinite development hiatus.
-          You can read more about it at:
-            #{Formatter.url("https://github.com/MacRuby/MacRuby")}
+          MacRuby has been discontinued. Consider RubyMotion:
+            brew cask install rubymotion
         EOS
         when /(lib)?lzma/ then <<~EOS
-          lzma is now part of the xz formula, and can be installed with:
+          lzma is now part of the xz formula:
             brew install xz
         EOS
         when "gtest", "googletest", "google-test" then <<~EOS
@@ -58,10 +58,11 @@ module Homebrew
           ruin SSH's security.
         EOS
         when "gsutil" then <<~EOS
-          Install gsutil with `pip2 install gsutil`
+          gsutil is available through pip:
+            pip2 install gsutil
         EOS
         when "gfortran" then <<~EOS
-          GNU Fortran is now part of the GCC formula, and can be installed with:
+          GNU Fortran is part of the GCC formula:
             brew install gcc
         EOS
         when "play" then <<~EOS
@@ -73,9 +74,16 @@ module Homebrew
             #{Formatter.url("https://www.playframework.com/documentation/2.3.x/Highlights23")}
         EOS
         when "haskell-platform" then <<~EOS
-          We no longer package haskell-platform. Consider installing ghc,
-          cabal-install and stack instead:
-            brew install ghc cabal-install stack
+          The components of the Haskell Platform are available separately.
+
+          Glasgow Haskell Compiler:
+            brew install ghc
+
+          Cabal build system:
+            brew install cabal-install
+
+          Haskell Stack tool:
+            brew install haskell-stack
         EOS
         when "mysqldump-secure" then <<~EOS
           The creator of mysqldump-secure tried to game our popularity metrics.
@@ -87,9 +95,13 @@ module Homebrew
             brew cask install ngrok
         EOS
         when "cargo" then <<~EOS
-          cargo is part of the rust formula, and can be installed with:
+          cargo is part of the rust formula:
             brew install rust
         EOS
+        when "uconv" then <<~EOS
+          uconv is part of the icu4c formula:
+            brew install icu4c
+        EOS
         end
       end
       alias generic_blacklisted_reason blacklisted_reason