scsh: add HEAD

Closes Homebrew/homebrew#19071.

Signed-off-by: Jack Nagel <jacknagel@gmail.com>

Formula/scsh.rb

@@ -5,9 +5,21 @@ class Scsh < Formula
   url 'http://ftp.scsh.net/pub/scsh/0.6/scsh-0.6.7.tar.gz'
   sha1 'a1eaf0d0593e14914824898a0c3ec166429affd7'
 
+  head 'https://github.com/scheme/scsh.git'
+
+  if build.head?
+    depends_on 'automake' => :build
+    depends_on 'scheme48'
+  end
+
   def install
-    # will not build 64-bit
-    ENV.m32
+    if build.head?
+      system "autoreconf"
+    else
+      # will not build 64-bit
+      ENV.m32
+    end
+
     # build system is not parallel-safe
     ENV.deparallelize
     system "./configure", "--disable-debug", "--disable-dependency-tracking",