Issue #26014: Guide 2.7 users to the new packaging documentation:
- the top-level 2.7 docs page now links to the newer doc pages
  (installing and distribution) rather than the legacy ones
- the legacy install and distutils pages are now labeled as "legacy"
- the library/distutils page is updated to match the 3.x version
- "See also" links to the new docs are now provided in the legacy pages
- links to setuptools documentation have been updated

(original patch by Susan Sun)
diff --git a/Doc/library/distutils.rst b/Doc/library/distutils.rst
index 534faab..12ad8c0 100644
--- a/Doc/library/distutils.rst
+++ b/Doc/library/distutils.rst
@@ -1,10 +1,9 @@
-
 :mod:`distutils` --- Building and installing Python modules
 ===========================================================
 
 .. module:: distutils
-   :synopsis: Support for building and installing Python modules into an existing Python
-              installation.
+   :synopsis: Support for building and installing Python modules into an
+              existing Python installation.
 .. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org>
 
 
@@ -13,18 +12,31 @@
 100%-pure Python, or may be extension modules written in C, or may be
 collections of Python packages which include modules coded in both Python and C.
 
-This package is discussed in two separate chapters:
+Most Python users will *not* want to use this module directly, but instead
+use the cross-version tools maintained by the Python Packaging Authority. In
+particular,
+`setuptools <https://setuptools.readthedocs.io/en/latest/>`__ is an
+enhanced alternative to :mod:`distutils` that provides:
 
+* support for declaring project dependencies
+* additional mechanisms for configuring which files to include in source
+  releases (including plugins for integration with version control systems)
+* the ability to declare project "entry points", which can be used as the
+  basis for application plugin systems
+* the ability to automatically generate Windows command line executables at
+  installation time rather than needing to prebuild them
+* consistent behaviour across all supported Python versions
 
-.. seealso::
+The recommended `pip <https://pip.pypa.io/>`__ installer runs all
+``setup.py`` scripts with ``setuptools``, even if the script itself only
+imports ``distutils``. Refer to the
+`Python Packaging User Guide <https://packaging.python.org>`_ for more
+information.
 
-   :ref:`distutils-index`
-      The manual for developers and packagers of Python modules.  This describes how
-      to prepare :mod:`distutils`\ -based packages so that they may be easily
-      installed into an existing Python installation.
+For the benefits of packaging tool authors and users seeking a deeper
+understanding of the details of the current packaging and distribution
+system, the legacy :mod:`distutils` based user documentation and API
+reference remain available:
 
-   :ref:`install-index`
-      An "administrators" manual which includes information on installing modules into
-      an existing Python installation. You do not need to be a Python programmer to
-      read this manual.
-
+* :ref:`install-index`
+* :ref:`distutils-index`