mpich2: add --devel and --HEAD versions

Closes Homebrew/homebrew#12303.

Signed-off-by: Charlie Sharpsteen <source@sharpsteen.net>

Formula/mpich2.rb

@@ -4,7 +4,21 @@ class Mpich2 < Formula
   homepage 'http://www.mcs.anl.gov/research/projects/mpich2/index.php'
   url 'http://www.mcs.anl.gov/research/projects/mpich2/downloads/tarballs/1.4.1p1/mpich2-1.4.1p1.tar.gz'
   version '1.4.1p1'
-  md5 'b470666749bcb4a0449a072a18e2c204'
+  sha1 '8dcc8888fb27232eb8f76c11cc890f1c3c483804'
+  head 'https://svn.mcs.anl.gov/repos/mpi/mpich2/trunk'
+
+  devel do
+    url 'http://www.mcs.anl.gov/research/projects/mpich2/downloads/tarballs/1.5b1/mpich2-1.5b1.tar.gz'
+    version '1.5b1'
+    sha1 'd9dfc992657c3cbe5b40374fd8aaa553ebaf5402'
+  end
+
+  # the HEAD version requires the autotools to be installed
+  # (autoconf>=2.67, automake>=1.11, libtool>=2.4)
+  if ARGV.build_head?
+    depends_on 'automake' => :build
+    depends_on 'libtool'  => :build
+  end
 
   def options
     [
@@ -13,6 +27,18 @@ class Mpich2 < Formula
   end
 
   def install
+    unless ARGV.build_devel? or ARGV.build_head?
+      # parallel builds are broken prior to version 1.5a1
+      ENV.deparallelize
+    end
+
+    if ARGV.build_head?
+      # ensure that the consistent set of autotools built by homebrew is used to
+      # build MPICH2, otherwise very bizarre build errors can occur
+      ENV['MPICH2_AUTOTOOLS_DIR'] = (HOMEBREW_PREFIX+'bin')
+      system "./autogen.sh"
+    end
+
     args = [
       "--prefix=#{prefix}",
       "--mandir=#{man}",