Remove unecessary .fetch file from fetchable deps

lib/mix/lib/mix/compilers/elixir.ex

@@ -68,7 +68,7 @@ defmodule Mix.Compilers.Elixir do
         do: [Mix.Project | stale],
         else: stale
 
-    # If the lock has changed or a local dependency was added ore removed,
+    # If the lock has changed or a local dependency was added or removed,
     # we need to traverse lock/config files.
     deps_changed? =
       Mix.Utils.stale?([Mix.Project.config_mtime()], [modified]) or

lib/mix/lib/mix/dep/fetcher.ex

@@ -65,17 +65,7 @@ defmodule Mix.Dep.Fetcher do
           end
 
         if new do
-          # There is a race condition where if you compile deps
-          # and then immediately update them, we would not detect
-          # a mismatch with .mix/compile.fetch, so we go ahead and
-          # delete all of them.
-          Mix.Project.build_path()
-          |> Path.dirname()
-          |> Path.join("*/lib/#{dep.app}/.mix/compile.fetch")
-          |> Path.wildcard(match_dot: true)
-          |> Enum.each(&File.rm/1)
-
-          File.touch!(Path.join(opts[:dest], ".fetch"))
+          mark_as_fetched([dep])
           dep = put_in(dep.opts[:lock], new)
           {dep, [app | acc], Map.put(lock, app, new)}
         else
@@ -123,14 +113,16 @@ defmodule Mix.Dep.Fetcher do
   end
 
   defp mark_as_fetched(deps) do
-    # If the dependency is fetchable, we are going to write a .fetch
-    # file to it. Each build, regardless of the environment and location,
-    # will compared against this .fetch file to know if the dependency
-    # needs recompiling.
-    _ =
-      for %Mix.Dep{scm: scm, opts: opts} <- deps, scm.fetchable?() do
-        File.touch!(Path.join(opts[:dest], ".fetch"))
-      end
+    build_path =
+      Mix.Project.build_path()
+      |> Path.dirname()
+
+    for %Mix.Dep{app: app, scm: scm} <- deps, scm.fetchable?() do
+      build_path
+      |> Path.join("*/lib/#{app}/.mix/compile.fetch")
+      |> Path.wildcard(match_dot: true)
+      |> Enum.each(&File.rm/1)
+    end
 
     :ok
   end

lib/mix/lib/mix/dep/loader.ex

@@ -403,15 +403,7 @@ defmodule Mix.Dep.Loader do
   end
 
   defp recently_fetched?(%Mix.Dep{opts: opts, scm: scm}) do
-    scm.fetchable?() &&
-      Mix.Utils.stale?(
-        join_stale(opts, :dest, ".fetch"),
-        join_stale(opts, :build, ".mix/compile.fetch")
-      )
-  end
-
-  defp join_stale(opts, key, file) do
-    [Path.join(opts[key], file)]
+    scm.fetchable?() and not File.exists?(Path.join(opts[:build], ".mix/compile.fetch"))
   end
 
   defp app_status(app_path, app, req) do

lib/mix/test/mix/tasks/deps.git_test.exs

@@ -147,17 +147,17 @@ defmodule Mix.Tasks.DepsGitTest do
       assert_received {:mix_shell, :info, [^message]}
 
       assert File.exists?("deps/deps_on_git_repo/mix.exs")
-      assert File.rm("deps/deps_on_git_repo/.fetch") == :ok
       assert File.exists?("deps/git_repo/mix.exs")
-      assert File.rm("deps/git_repo/.fetch") == :ok
 
       # Compile the dependencies
       Mix.Tasks.Deps.Compile.run([])
+      assert File.exists?("_build/dev/lib/deps_on_git_repo/.mix/compile.fetch")
+      assert File.exists?("_build/dev/lib/git_repo/.mix/compile.fetch")
 
       # Now update children and make sure it propagates
       Mix.Tasks.Deps.Update.run(["git_repo"])
-      assert File.exists?("deps/deps_on_git_repo/.fetch")
-      assert File.exists?("deps/git_repo/.fetch")
+      refute File.exists?("_build/dev/lib/deps_on_git_repo/.mix/compile.fetch")
+      refute File.exists?("_build/dev/lib/git_repo/.mix/compile.fetch")
 
       # Clear tasks to recompile Git repo but unload it so...
       purge([GitRepo])

lib/mix/test/mix/tasks/deps.path_test.exs

@@ -27,16 +27,6 @@ defmodule Mix.Tasks.DepsPathTest do
     end
   end
 
-  @tag apps: [:raw_sample]
-  test "does not mark for compilation on get/update" do
-    in_fixture("deps_status", fn ->
-      Mix.Project.push(DepsApp)
-
-      Mix.Tasks.Deps.Get.run(["--all"])
-      refute File.exists?("custom/raw_repo/.fetch")
-    end)
-  end
-
   @tag apps: [:raw_sample]
   test "compiles and runs even if lock does not match" do
     in_fixture("deps_status", fn ->