DASH Shell: Added HEAD option.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/dash.rb

@@ -4,10 +4,15 @@ class Dash <Formula
   url 'http://gondor.apana.org.au/~herbert/dash/files/dash-0.5.6.1.tar.gz'
   homepage 'http://gondor.apana.org.au/~herbert/dash/'
   sha1 '06944456a1e3a2cbc325bffd0c898eff198b210a'
+  head 'https://git.kernel.org/pub/scm/utils/dash/dash.git', :using => :git
 
   def install
-    system "./configure", "--disable-debug",
-                          "--prefix=#{prefix}",
+    if ARGV.build_head?
+      system "aclocal"
+      system "autoreconf -f -i -Wall,no-obsolete"
+    end
+
+    system "./configure", "--prefix=#{prefix}",
                           "--with-libedit"
     system "make"
     system "make install"