Consolidate sudo checks.

Closes Homebrew/homebrew#20318.

Library/Homebrew/cmd/install.rb

@@ -18,10 +18,6 @@ module Homebrew extend self
       end
     end unless ARGV.force?
 
-    if Process.uid.zero? and not File.stat(HOMEBREW_BREW_FILE).uid.zero?
-      raise "Cowardly refusing to `sudo brew install'\n#{SUDO_BAD_ERRMSG}"
-    end
-
     install_formulae ARGV.formulae
   end
 

Library/Homebrew/cmd/link.rb

@@ -5,10 +5,6 @@ module Homebrew extend self
   def link
     raise KegUnspecifiedError if ARGV.named.empty?
 
-    if Process.uid.zero? and not File.stat(HOMEBREW_BREW_FILE).uid.zero?
-      raise "Cowardly refusing to `sudo brew link'\n#{SUDO_BAD_ERRMSG}"
-    end
-
     mode = OpenStruct.new
 
     mode.overwrite = true if ARGV.include? '--overwrite'

Library/Homebrew/cmd/pin.rb

@@ -2,9 +2,6 @@ require 'formula'
 
 module Homebrew extend self
   def pin
-    if Process.uid.zero? and not File.stat(HOMEBREW_BREW_FILE).uid.zero?
-      abort "Cowardly refusing to `sudo pin'"
-    end
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
     ARGV.formulae.each do |f|

Library/Homebrew/cmd/unpin.rb

@@ -2,9 +2,6 @@ require 'formula'
 
 module Homebrew extend self
   def unpin
-    if Process.uid.zero? and not File.stat(HOMEBREW_BREW_FILE).uid.zero?
-      abort "Cowardly refusing to `sudo unpin'"
-    end
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
     ARGV.formulae.each do |f|

Library/Homebrew/cmd/upgrade.rb

@@ -8,12 +8,6 @@ end
 
 module Homebrew extend self
   def upgrade
-    if Process.uid.zero? and not File.stat(HOMEBREW_BREW_FILE).uid.zero?
-      # note we only abort if Homebrew is *not* installed as sudo and the user
-      # calls brew as root. The fix is to chown brew to root.
-      abort "Cowardly refusing to `sudo brew upgrade'"
-    end
-
     Homebrew.perform_preinstall_checks
 
     if ARGV.named.empty?

Library/Homebrew/exceptions.rb

@@ -213,11 +213,3 @@ class ChecksumMismatchError < RuntimeError
     super + advice.to_s
   end
 end
-
-module Homebrew extend self
-  SUDO_BAD_ERRMSG = <<-EOS.undent
-    You can use brew with sudo, but only if the brew executable is owned by root.
-    However, this is both not recommended and completely unsupported so do so at
-    your own risk.
-  EOS
-end

Library/Homebrew/global.rb

@@ -99,3 +99,9 @@ HOMEBREW_PULL_OR_COMMIT_URL_REGEX = 'https:\/\/github.com\/(\w+)\/homebrew(-\w+)
 require 'compat' unless ARGV.include? "--no-compat" or ENV['HOMEBREW_NO_COMPAT']
 
 ORIGINAL_PATHS = ENV['PATH'].split(':').map{ |p| Pathname.new(p).expand_path rescue nil }.compact.freeze
+
+SUDO_BAD_ERRMSG = <<-EOS.undent
+  You can use brew with sudo, but only if the brew executable is owned by root.
+  However, this is both not recommended and completely unsupported so do so at
+  your own risk.
+EOS

Library/brew.rb

@@ -58,17 +58,17 @@ end
 begin
   trap("INT", std_trap) # restore default CTRL-C handler
 
-  aliases = {'ls' => :list,
-             'homepage' => :home,
-             '-S' => :search,
-             'up' => :update,
-             'ln' => :link,
-             'instal' => :install, # gem does the same
-             'rm' => :uninstall,
-             'remove' => :uninstall,
-             'configure' => :diy,
-             'abv' => :info,
-             'dr' => :doctor,
+  aliases = {'ls' => 'list',
+             'homepage' => 'home',
+             '-S' => 'search',
+             'up' => 'update',
+             'ln' => 'link',
+             'instal' => 'install', # gem does the same
+             'rm' => 'uninstall',
+             'remove' => 'uninstall',
+             'configure' => 'diy',
+             'abv' => 'info',
+             'dr' => 'doctor',
              '--repo' => '--repository',
              'environment' => '--env'  # same as gem
              }
@@ -76,11 +76,19 @@ begin
   cmd = ARGV.shift
   cmd = aliases[cmd] if aliases[cmd]
 
-  if cmd == '-c1'
+  if cmd == '-c1' # Shortcut for one line of configuration
     cmd = '--config'
     ARGV.unshift('-1')
   end
 
+  sudo_check = Set.new %w[ install link pin unpin upgrade ]
+
+  if sudo_check.include? cmd
+    if Process.uid.zero? and not File.stat(HOMEBREW_BREW_FILE).uid.zero?
+      raise "Cowardly refusing to `sudo brew #{cmd}`\n#{SUDO_BAD_ERRMSG}"
+    end
+  end
+
   # Add example external commands to PATH before checking.
   ENV['PATH'] += ":#{HOMEBREW_REPOSITORY}/Library/Contributions/cmd"
   if require? HOMEBREW_REPOSITORY/"Library/Homebrew/cmd"/cmd