unfs3: add HEAD

Closes Homebrew/homebrew#24399.

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

Formula/unfs3.rb

@@ -4,9 +4,16 @@ class Unfs3 < Formula
   homepage 'http://unfs3.sourceforge.net'
   url 'http://downloads.sourceforge.net/project/unfs3/unfs3/0.9.22/unfs3-0.9.22.tar.gz'
   sha1 'a6c83e1210ce75836c672cd76e66577bfef7a17a'
+  head 'https://svn.code.sf.net/p/unfs3/code/trunk/'
+
+  if build.head?
+    depends_on "autoconf" => :build
+    depends_on "automake" => :build
+  end
 
   def install
     ENV.j1 # Build is not parallel-safe
+    system "./bootstrap" if build.head?
     system "./configure", "--disable-debug", "--disable-dependency-tracking",
                           "--prefix=#{prefix}"
     system "make"