Tap: make remote a separate method to reduce initial overhead

Also make remote method only response to installed tap.

Library/Homebrew/cmd/tap-info.rb

@@ -48,7 +48,7 @@ module Homebrew
           info += "Not installed"
         end
         puts info
-        puts "From: #{tap.remote}"
+        puts "From: #{tap.remote.nil? ? "N/A" : tap.remote}"
       end
     end
   end

Library/Homebrew/cmd/tap.rb

@@ -14,10 +14,11 @@ module Homebrew
   end
 
   def install_tap user, repo, clone_target=nil
-    tap = Tap.new user, repo, clone_target
+    tap = Tap.new user, repo
     return false if tap.installed?
     ohai "Tapping #{tap}"
-    args = %W[clone #{tap.remote} #{tap.path}]
+    remote = clone_target || "https://github.com/#{tap.user}/homebrew-#{tap.repo}"
+    args = %W[clone #{remote} #{tap.path}]
     args << "--depth=1" unless ARGV.include?("--full")
     safe_system "git", *args
 

Library/Homebrew/tap.rb

@@ -7,20 +7,26 @@ class Tap
   attr_reader :repo
   attr_reader :name
   attr_reader :path
-  attr_reader :remote
 
-  def initialize(user, repo, remote=nil)
+  def initialize(user, repo)
     # we special case homebrew so users don't have to shift in a terminal
     @user = user == "homebrew" ? "Homebrew" : user
     @repo = repo
     @name = "#{@user}/#{@repo}".downcase
     @path = TAP_DIRECTORY/"#{@user}/homebrew-#{@repo}".downcase
-    if installed?
+  end
+
+  def remote
+    @remote ||= if installed?
+      if (@path/".git").exist?
         @path.cd do
-        @remote = Utils.popen_read("git", "config", "--get", "remote.origin.url").chomp
+          Utils.popen_read("git", "config", "--get", "remote.origin.url").chomp
         end
       else
-      @remote = remote || "https://github.com/#{@user}/homebrew-#{@repo}"
+        nil
+      end
+    else
+      raise TapUnavailableError, name
     end
   end
 
@@ -46,7 +52,8 @@ class Tap
   end
 
   def custom_remote?
-    @remote.casecmp("https://github.com/#{@user}/homebrew-#{@repo}") != 0
+    return true unless remote
+    remote.casecmp("https://github.com/#{@user}/homebrew-#{@repo}") != 0
   end
 
   def formula_files
@@ -69,7 +76,7 @@ class Tap
       "user" => @user,
       "repo" => @repo,
       "path" => @path.to_s,
-      "remote" => @remote,
+      "remote" => remote,
       "installed" => installed?,
       "official" => official?,
       "custom_remote" => custom_remote?,