Fix trailing whitespace in files generated by "mix new" (#15710)

Author: rhcarvalho

lib/mix/lib/mix/tasks/new.ex

@@ -269,8 +269,8 @@ defmodule Mix.Tasks.New do
   embed_template(:readme, """
   # <%= @mod %>
 
-  **TODO: Add description**
-  <%= if @app do %>
+  **TODO: Add description**<%= if @app do %>
+
   ## Installation
 
   If [available in Hex](https://hex.pm/docs/publish), the package can be installed
@@ -286,8 +286,7 @@ defmodule Mix.Tasks.New do
 
   Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
   and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
-  be found at <https://<%= String.replace(@app, "_", "-") %>.hexdocs.pm>.
-  <% end %>
+  be found at <https://<%= String.replace(@app, "_", "-") %>.hexdocs.pm>.<% end %>
   """)
 
   embed_template(:formatter, """
@@ -325,11 +324,10 @@ defmodule Mix.Tasks.New do
   erl_crash.dump
 
   # Also ignore archive artifacts (built via "mix archive.build").
-  *.ez
-  <%= if @app do %>
+  *.ez<%= if @app do %>
+
   # Ignore package tarball (built via "mix hex.build").
-  <%= @app %>-*.tar
-  <% end %>
+  <%= @app %>-*.tar<% end %>
   """)
 
   embed_template(:mix_exs, """

lib/mix/test/mix/tasks/new_test.exs

@@ -16,8 +16,16 @@ defmodule Mix.Tasks.NewTest do
         assert file =~ "version: \"0.1.0\""
       end)
 
-      assert_file("hello_world/README.md", ~r/# HelloWorld\n/)
-      assert_file("hello_world/.gitignore")
+      assert_file("hello_world/README.md", fn file ->
+        assert file =~ "# HelloWorld\n"
+        assert String.ends_with?(file, "\n")
+        refute String.ends_with?(file, "\n\n")
+      end)
+
+      assert_file("hello_world/.gitignore", fn file ->
+        assert String.ends_with?(file, "\n")
+        refute String.ends_with?(file, "\n\n")
+      end)
 
       assert_file("hello_world/lib/hello_world.ex", ~r/defmodule HelloWorld do/)
       assert_file("hello_world/test/test_helper.exs", ~r/ExUnit.start()/)
@@ -118,8 +126,16 @@ defmodule Mix.Tasks.NewTest do
         assert file =~ "apps_path: \"apps\""
       end)
 
-      assert_file("hello_world/README.md", ~r/# HelloWorld\n/)
-      assert_file("hello_world/.gitignore")
+      assert_file("hello_world/README.md", fn file ->
+        assert file =~ "# HelloWorld\n"
+        assert String.ends_with?(file, "\n")
+        refute String.ends_with?(file, "\n\n")
+      end)
+
+      assert_file("hello_world/.gitignore", fn file ->
+        assert String.ends_with?(file, "\n")
+        refute String.ends_with?(file, "\n\n")
+      end)
 
       assert_received {:mix_shell, :info, ["* creating mix.exs"]}