makefile2graph: New formula

Creates a graph of dependencies from GNU-Make;
Output is a graphiz-dot file or a Gexf-XML file.

Closes Homebrew/homebrew#33952

Formula/makefile2graph.rb

@@ -0,0 +1,32 @@
+require "formula"
+
+class Makefile2graph < Formula
+  homepage "https://github.com/lindenb/makefile2graph"
+  url "https://github.com/lindenb/makefile2graph/archive/stable1.2.tar.gz"
+  sha1 "fd6799c23e4b9599f4caf23b0ce0993ab33362a8"
+  head "https://github.com/lindenb/makefile2graph.git"
+
+  depends_on "graphviz" => :recommended
+
+  def install
+    system "make"
+    system "make", "test" if build.with? "graphviz"
+    bin.install "make2graph"
+    man1.install "make2graph.1"
+    doc.install "LICENSE", "README.md", "screenshot.png"
+  end
+
+  test do
+    (testpath/"Makefile").write <<-EOS.undent
+      all: foo
+      all: bar
+      foo: ook
+      bar: ook
+      ook:
+    EOS
+    system "make -Bnd >make-Bnd"
+    system "#{bin}/make2graph <make-Bnd"
+    system "#{bin}/make2graph --root <make-Bnd"
+    system "#{bin}/make2graph -x <make-Bnd"
+  end
+end