Rewrite of HOMEBREW_ folder locations

This rewrite attempts to sort out where the Prefix, Cellar, and
Repository are relative to the real and symlinked 'brew' command.

Also included is a --config option which dumps all of these variables.

Any top-level script must define a "BREW_FILE" that gives the path
to brew as it exists in the path. 'brew' itself just uses __FILE__ and
install.rb does a `which brew` (there may be a better way?)

The Prefix is always relative to the location of brew as it exists in
the path. Thus, whether or not /usr/local/bin/brew is a symlink or real
file, the Prefix is always /usr/local. If you have brew in some other
prefix, such as /nonstandard/bin/brew, then '/nonstandard/ will be
managed by brew instead.

The Repository, Cellar, and "Library/Homebrew" required code is always
found relative to the "real" path or brew. If brew is a real file in
/usr/local/bin/brew, then everything else will be found in /usr/local
and we'll expect a /usr/local/.git

Otherwise, we dereference brew's symlink and look for everything else
relative to that path instead.

Library/Homebrew/global.rb

@@ -28,6 +28,8 @@ require 'hardware'
 
 ARGV.extend(HomebrewArgvExtension)
 
+HOMEBREW_VERSION = 0.4
+HOMEBREW_WWW = 'http://bit.ly/Homebrew'
 
 if Process.uid == 0
   # technically this is not the correct place, this cache is for *all users*
@@ -37,14 +39,9 @@ else
   HOMEBREW_CACHE=Pathname.new("~/Library/Caches/Homebrew").expand_path
 end
 
-HOMEBREW_PREFIX = (Pathname.getwd+__FILE__).dirname.parent.parent.cleanpath
-HOMEBREW_CELLAR = HOMEBREW_PREFIX+'Cellar'
-HOMEBREW_VERSION = 0.4
-HOMEBREW_WWW = 'http://bit.ly/Homebrew'
-
-# we use Library as we allow people to symlink their Homebrew into another
-# directory so they can hack in one place and use it in another
-HOMEBREW_REPOSITORY = (HOMEBREW_PREFIX+'Library').realpath.parent
+HOMEBREW_PREFIX = Pathname.new(BREW_FILE).dirname.parent # Where we link under
+HOMEBREW_REPOSITORY = Pathname.new(BREW_FILE).realpath.dirname.parent # Where .git is found
+HOMEBREW_CELLAR = HOMEBREW_REPOSITORY+'Cellar' # Where we build into
 
 MACOS_FULL_VERSION = `/usr/bin/sw_vers -productVersion`.chomp
 MACOS_VERSION = /(10\.\d+)(\.\d+)?/.match(MACOS_FULL_VERSION).captures.first.to_f

Library/Homebrew/install.rb

@@ -1,4 +1,6 @@
 #!/usr/bin/ruby
+BREW_FILE = `which brew`.strip
+
 require 'global'
 
 require 'brew.h'
@@ -8,6 +10,7 @@ require 'formula'
 require 'hardware'
 require 'keg'
 
+
 show_summary_heading = false
 
 def text_for_keg_only_formula f

bin/brew

@@ -5,16 +5,14 @@
 # odd exceptions. Reduce our support burden by showing a user-friendly error.
 Dir.getwd rescue abort "The current working directory doesn't exist, cannot proceed."
 
+BREW_FILE = __FILE__
+
 def homebrew_rubylib_path
   lib_path = "/../../Library/Homebrew"
-  # we resolve off of Dir.getwd as otherwise the symlink gets resolved!
-  brew_path = if not File.symlink? __FILE__ or File.exist? Dir.getwd+'/'+__FILE__+lib_path
-    # standard 100% symlinked or non-symlinked installation
-    __FILE__
-  else
-    # non-standard installation -- just this script is symlinked
-    File.readlink(__FILE__)
-  end
+
+  # Library/Homebrew is relative to the real path of brew
+  brew_path = __FILE__
+  brew_path = File.readlink(brew_path) if File.symlink? brew_path
   return File.expand_path(brew_path+lib_path)
 end
 
@@ -53,12 +51,36 @@ case Hardware.cpu_type when :ppc, :dunno
   abort "Sorry, Homebrew does not support your computer's CPU architecture."
 end
 
+def dump_config
+  puts <<-EOS
+HOMEBREW_VERSION:    #{HOMEBREW_VERSION}
+
+HOMEBREW_PREFIX:     #{HOMEBREW_PREFIX}
+\tWhere do we symlink installs to?
+
+HOMEBREW_CELLAR:     #{HOMEBREW_CELLAR}
+\tWhere do we store our built products?
+
+HOMEBREW_CACHE:      #{HOMEBREW_CACHE}
+\tWhere do we cache our downloads?
+
+HOMEBREW_REPOSITORY: #{HOMEBREW_REPOSITORY}
+\tWhere is our .git?
+
+library path:        #{homebrew_rubylib_path}
+\tWhat do we put on the ruby path?
+EOS
+end
+
+
 begin
   require 'brew.h'
 
   case ARGV.shift
   when '--prefix'
     puts HOMEBREW_PREFIX
+  when '--config'
+    dump_config
 
     when 'home', 'homepage'
       if ARGV.named_empty?
@@ -83,7 +105,7 @@ begin
       end
 
     when 'search', '-S'
-      formulae = (HOMEBREW_PREFIX+'Library'+'Formula').children.sort.map{|f| f.basename('.rb') }
+      formulae = (HOMEBREW_REPOSITORY+'Library/Formula').children.sort.map{|f| f.basename('.rb') }
       if ARGV.first =~ /^\/(.*)\/$/
         puts_columns formulae.grep(Regexp.new($1))
       else
@@ -95,9 +117,9 @@ begin
         # EDITOR isn't a good fit here, we need a GUI client that actually has
         # a UI for projects, so apologies if this wasn't what you expected,
         # please improve it! :)
-        exec 'mate', *Dir["#{HOMEBREW_PREFIX}/Library/*"]<<
-                          "#{HOMEBREW_PREFIX}/bin/brew"<<
-                          "#{HOMEBREW_PREFIX}/README.md"
+        exec 'mate', *Dir["#{HOMEBREW_REPOSITORY}/Library/*"]<<
+                          "#{HOMEBREW_REPOSITORY}/bin/brew"<<
+                          "#{HOMEBREW_REPOSITORY}/README.md"
       else
         exec_editor *ARGV.formulae.collect {|f| f.path}
       end
@@ -108,6 +130,9 @@ begin
         exit 0
       end
       
+      # The Cellar lives under the repository
+      raise "Cannot write to #{HOMEBREW_REPOSITORY}" unless HOMEBREW_REPOSITORY.writable?
+      # The Prefix is where we symlink under
       raise "Cannot write to #{HOMEBREW_PREFIX}" unless HOMEBREW_PREFIX.writable?
 
       if ARGV.interactive? and ARGV.formulae.length > 1