Add md5 on 'brew create' if we can figure it out.

Library/Homebrew/brew.h.rb

@@ -26,6 +26,7 @@ end
 
 def __make url, name
   require 'formula'
+  require 'digest'
 
   path = Formula.path name
   raise "#{path} already exists" if path.exist?
@@ -45,13 +46,26 @@ def __make url, name
     puts "Version detected as #{version}."
   end
 
+  md5 = ''
+  if ARGV.include? "--cache" and version != nil
+    strategy = detect_download_strategy url
+    if strategy == CurlDownloadStrategy
+      d = strategy.new url, name, version, nil
+      the_tarball = d.fetch
+      md5 = Digest::MD5.hexdigest(the_tarball.read)
+      puts "MD5 is #{md5}"
+    else
+      puts "--cache requested, but we can only cache formulas that use Curl."
+    end
+  end
+
   template=<<-EOS
             require 'formula'
 
             class #{Formula.class_s name} <Formula
               url '#{url}'
               homepage ''
-              md5 ''
+              md5 '#{md5}'
 
   cmake       depends_on 'cmake'
 

Library/Homebrew/download_strategy.rb

@@ -287,3 +287,19 @@ class BazaarDownloadStrategy <AbstractDownloadStrategy
     end
   end
 end
+
+def detect_download_strategy url
+  case url
+  when %r[^cvs://] then CVSDownloadStrategy
+  when %r[^hg://] then MercurialDownloadStrategy
+  when %r[^svn://] then SubversionDownloadStrategy
+  when %r[^svn+http://] then SubversionDownloadStrategy
+  when %r[^git://] then GitDownloadStrategy
+  when %r[^bzr://] then BazaarDownloadStrategy
+  when %r[^https?://(.+?\.)?googlecode\.com/hg] then MercurialDownloadStrategy
+  when %r[^https?://(.+?\.)?googlecode\.com/svn] then SubversionDownloadStrategy
+  when %r[^https?://(.+?\.)?sourceforge\.net/svnroot/] then SubversionDownloadStrategy
+  when %r[^http://svn.apache.org/repos/] then SubversionDownloadStrategy
+  else CurlDownloadStrategy
+  end
+end

Library/Homebrew/formula.rb

@@ -134,19 +134,7 @@ class Formula
   
   # reimplement if we don't autodetect the download strategy you require
   def download_strategy
-    case url
+    detect_download_strategy url
-    when %r[^cvs://] then CVSDownloadStrategy
-    when %r[^hg://] then MercurialDownloadStrategy
-    when %r[^svn://] then SubversionDownloadStrategy
-    when %r[^svn+http://] then SubversionDownloadStrategy
-    when %r[^git://] then GitDownloadStrategy
-    when %r[^bzr://] then BazaarDownloadStrategy
-    when %r[^https?://(.+?\.)?googlecode\.com/hg] then MercurialDownloadStrategy
-    when %r[^https?://(.+?\.)?googlecode\.com/svn] then SubversionDownloadStrategy
-    when %r[^https?://(.+?\.)?sourceforge\.net/svnroot/] then SubversionDownloadStrategy
-    when %r[^http://svn.apache.org/repos/] then SubversionDownloadStrategy
-    else CurlDownloadStrategy
-    end
   end
 
   # tell the user about any caveats regarding this package, return a string