untap: Handle multiple arguments

Closes Homebrew/homebrew#36436.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Library/Homebrew/cmd/tap.rb

@@ -108,8 +108,8 @@ module Homebrew
     end
   end
 
-  def tap_args
-    ARGV.first =~ HOMEBREW_TAP_ARGS_REGEX
+  def tap_args(tap_name=ARGV.first)
+    tap_name =~ HOMEBREW_TAP_ARGS_REGEX
     raise "Invalid tap name" unless $1 && $3
     [$1, $3]
   end

Library/Homebrew/cmd/untap.rb

@@ -4,7 +4,8 @@ module Homebrew
   def untap
     raise "Usage is `brew untap <tap-name>`" if ARGV.empty?
 
-    user, repo = tap_args
+    ARGV.each do |tapname|
+      user, repo = tap_args(tapname)
 
       # we consistently downcase in tap to ensure we are not bitten by case-insensive
       # filesystem issues. Which is the default on mac. The problem being the
@@ -24,6 +25,7 @@ module Homebrew
       tapd.dirname.rmdir_if_possible
       puts "Untapped #{files.length} formula#{plural(files.length, 'e')}"
     end
+  end
 
   def unlink_tap_formula paths
     untapped = 0