Add disclaimer about loadpaths (#1000)

lib/mix/tasks/hex.audit.ex

@@ -11,6 +11,10 @@ defmodule Mix.Tasks.Hex.Audit do
   maintainers. The task will display a message describing
   the reason for retirement and exit with a non-zero code
   if any retired dependencies are found.
+
+  > In a project, this task must be invoked before any other tasks
+  > that may load or start your application. Otherwise, you must
+  > explicitly list `:hex` as part of your `:extra_applications`.
   """
 
   @behaviour Hex.Mix.TaskDescription

lib/mix/tasks/hex.build.ex

@@ -14,6 +14,10 @@ defmodule Mix.Tasks.Hex.Build do
 
   #{Hex.Package.configuration_doc()}
 
+  > In a project, this task must be invoked before any other tasks
+  > that may load or start your application. Otherwise, you must
+  > explicitly list `:hex` as part of your `:extra_applications`.
+
   ### Command line options
 
     * `--unpack` - Builds the tarball and unpacks contents into a directory.

lib/mix/tasks/hex.outdated.ex

@@ -35,6 +35,10 @@ defmodule Mix.Tasks.Hex.Outdated do
   be updated that in turn update their own dependencies, which may cause the
   package you want to update to not be able to update.
 
+  > In a project, this task must be invoked before any other tasks
+  > that may load or start your application. Otherwise, you must
+  > explicitly list `:hex` as part of your `:extra_applications`.
+
   ## Command line options
 
     * `--all` - shows all outdated packages, including children of packages defined in `mix.exs`