Move --version logic into cmd/--version.rb.

Library/Homebrew/brew.rb

@@ -22,12 +22,6 @@ end
 
 require "global"
 
-if ARGV == %w[--version] || ARGV == %w[-v]
-  puts "Homebrew #{HOMEBREW_VERSION}"
-  puts "Homebrew/homebrew-core #{CoreTap.instance.version_string}"
-  exit 0
-end
-
 begin
   trap("INT", std_trap) # restore default CTRL-C handler
 

Library/Homebrew/brew.sh

@@ -232,6 +232,7 @@ case "$HOMEBREW_COMMAND" in
   --repo)      HOMEBREW_COMMAND="--repository" ;;
   environment) HOMEBREW_COMMAND="--env" ;;
   --config)    HOMEBREW_COMMAND="config" ;;
+  -v)          HOMEBREW_COMMAND="--version" ;;
 esac
 
 if [[ "$HOMEBREW_COMMAND" = "cask" ]]

Library/Homebrew/cmd/--version.rb

@@ -5,10 +5,9 @@ module Homebrew
   module_function
 
   def __version
-    # As a special case, `--version` is implemented directly in `brew.rb`. This
-    # file merely serves as a container for the documentation. It also catches
-    # the case where running `brew --version` with additional arguments would
-    # produce a rather cryptic message about a non-existent `--version` command.
-    raise UsageError
+    odie "This command does not take arguments." if ARGV.any?
+
+    puts "Homebrew #{HOMEBREW_VERSION}"
+    puts "Homebrew/homebrew-core #{CoreTap.instance.version_string}"
   end
 end

Library/Homebrew/global.rb

@@ -83,6 +83,7 @@ HOMEBREW_INTERNAL_COMMAND_ALIASES = {
   "--repo" => "--repository",
   "environment" => "--env",
   "--config" => "config",
+  "-v" => "--version",
 }.freeze
 
 require "set"