More informative message for DOT tree generation (#4791)

Signed-off-by: José Valim <[email protected]>

Author: Josh Price

lib/mix/lib/mix/tasks/app.tree.ex

@@ -57,8 +57,13 @@ defmodule Mix.Tasks.App.Tree do
     if opts[:format] == "dot" do
       Mix.Utils.write_dot_graph!("app_tree.dot", "application tree",
                                  {:normal, app}, callback, opts)
-      Mix.shell.info "Generated \"app_tree.dot\" in current directory.\n" <>
-                     "You can use http://www.graphviz.org/ to open it."
+      Mix.shell.info """
+        Generated "app_tree.dot" in the current directory. To generate a PNG:
+
+           dot -Tpng app_tree.dot -o app_tree.png
+
+        For more options see http://www.graphviz.org/.
+        """ |> String.strip
     else
       Mix.Utils.print_tree({:normal, app}, callback, opts)
     end

lib/mix/lib/mix/tasks/deps.tree.ex

@@ -52,8 +52,13 @@ defmodule Mix.Tasks.Deps.Tree do
     if opts[:format] == "dot" do
       callback = callback(&format_dot/1, deps, opts)
       Mix.Utils.write_dot_graph!("deps_tree.dot", "dependency tree", root, callback, opts)
-      Mix.shell.info "Generated \"deps_tree.dot\" in current directory.\n" <>
-                     "You can use http://www.graphviz.org/ to open it."
+      Mix.shell.info """
+        Generated "deps_tree.dot" in the current directory. To generate a PNG:
+
+            dot -Tpng deps_tree.dot -o deps_tree.png
+
+        For more options see http://www.graphviz.org/.
+        """ |> String.strip
     else
       callback = callback(&format_tree/1, deps, opts)
       Mix.Utils.print_tree(root, callback, opts)

lib/mix/lib/mix/utils.ex

@@ -214,7 +214,7 @@ defmodule Mix.Utils do
         {"", seen}
       %{} when is_nil(edge_info) ->
         {~s(  "#{parent}" -> "#{name}"\n),
-         Map.put(seen, key, true),}
+         Map.put(seen, key, true)}
       %{} ->
         {~s(  "#{parent}" -> "#{name}" [label=\"#{edge_info}\"]\n),
          Map.put(seen, key, true)}