Add alias support to formulae

* brew install will find an aliased formula
* aliases are searched against
* warn when creating a new formula that has an existing alias.

If Subversion has an alias "svn", then warn when the user tries to
create a new formula "svn". The formula can still be created, though
the user should make sure it's not a duplicate of the existing
aliased one.

Subversion and Objective-Caml formulas get some alises here, so we have
something to test against.

2 files changed, 41 insertions, 2 deletions

diff --git a/Library/Homebrew/brew.h.rb b/Library/Homebrew/brew.h.rb
index d8ab4305e..b0b795999 100644
--- a/Library/Homebrew/brew.h.rb
+++ b/Library/Homebrew/brew.h.rb
@@ -29,6 +29,13 @@ def __make url, name
 
   path = Formula.path name
   raise "#{path} already exists" if path.exist?
+  
+  # Check if a formula aliased to this name exists.
+  already_aka = Formulary.find_alias name
+  if already_aka != nil
+    opoo "Formula #{already_aka} is aliased to #{name}."
+    puts "Please check if you are creating a duplicate."
+  end
 
   template=<<-EOS
             require 'formula'
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 0cc084705..029aef77c 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -52,6 +52,22 @@ class Formulary
       yield name, klass
     end
   end
+
+  def self.get_aliases
+    aliases = {}
+    Formulary.read_all do |name, klass|
+      aka = klass.aliases
+      next if aka == nil
+
+      aka.each {|item| aliases[item.to_s] = name }
+    end
+    return aliases
+  end
+  
+  def self.find_alias name
+    aliases = Formulary.get_aliases
+    return aliases[name]
+  end
 end
 
 
@@ -225,7 +241,15 @@ class Formula
       require name
       name = path.stem
     else
-      require self.path(name)
+      begin
+        require self.path(name)
+      rescue LoadError => e
+        # Couldn't find formula 'name', so look for an alias.
+        real_name = Formulary.find_alias name
+        raise e if real_name == nil
+        puts "#{name} is an alias for #{real_name}"
+        name = real_name
+      end
     end
     begin
       klass_name =self.class_s(name)
@@ -418,7 +442,7 @@ private
       end
     end
 
-    attr_rw :url, :version, :homepage, :specs, :deps, *CHECKSUM_TYPES
+    attr_rw :url, :version, :homepage, :specs, :deps, :aliases, *CHECKSUM_TYPES
 
     def head val=nil, specs=nil
       if specs
@@ -426,6 +450,14 @@ private
       end
       val.nil? ? @head : @head = val
     end
+    
+    def aka *args
+      @aliases ||= []
+
+      args.each do |item|
+        @aliases << item.to_s
+      end
+    end
 
     def depends_on name, *args
       @deps ||= []