when: use a stable tarball

Closes Homebrew/homebrew#19171.

Formula/when.rb

@@ -2,12 +2,16 @@ require 'formula'
 
 class When < Formula
   homepage 'http://www.lightandmatter.com/when/when.html'
-  url 'http://www.lightandmatter.com/when/when.tar.gz'
-  sha1 '1bd6d8e1cb40ccc30a61ac8b22376d42fe6b2f2b'
-  version '1.1.31'
+  url 'http://www.lightandmatter.com/when/when_1.1.31-debian-source.tar.gz'
+  sha1 '2d986aadac5667b7eb50940a6aa547d50c9f8f82'
 
   def install
-    bin.install 'when'
-    man1.install 'when.1'
+    # Double-gzipped.
+    system "tar xvf when_1.1.31.orig.tar.gz"
+    cd "when-1.1.31" do
+      prefix.install_metafiles
+      bin.install 'when'
+      man1.install 'when.1'
+    end
   end
 end