doc: west: move manifest command docs to manifest.rst

This is just a prep work commit for documenting ``west manifest
--merge``.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>

doc/guides/west/manifest.rst

@@ -3,10 +3,10 @@
 West Manifests
 ##############
 
-This page contains detailed information about west's multiple repository model
+This page contains detailed information about west's multiple repository model,
-and manifest files. For API documentation on the ``west.manifest`` module, see
+manifest files, and the ``west manifest`` command. For API documentation on the
-:ref:`west-apis-manifest`. For a more general introduction and command
+``west.manifest`` module, see :ref:`west-apis-manifest`. For a more general
-overview, see :ref:`west-multi-repo`.
+introduction and command overview, see :ref:`west-multi-repo`.
 
 .. _west-mr-model:
 
@@ -271,3 +271,29 @@ repository root.
 
 The pykwalify schema :file:`manifest-schema.yml` in the west source code
 repository is used to validate the manifest section.
+
+.. _west-manifest-cmd:
+
+Manifest Command
+****************
+
+The ``west manifest`` command can be used to manipulate manifest files.
+It takes an action, and action-specific arguments.
+
+The following sections describe each action and provides a basic signature for
+simple uses. Run ``west manifest --help`` for full details on all options.
+
+Freezing Manifests
+==================
+
+The ``--freeze`` action outputs a frozen manifest:
+
+.. code-block:: none
+
+   west manifest --freeze [-o outfile]
+
+A "frozen" manifest is a manifest file where every project's revision is a SHA.
+You can use ``--freeze`` to produce a frozen manifest that's equivalent to your
+current manifest file. The ``-o`` option specifies an output file; if not
+given, standard output is used.
+

doc/guides/west/repo-tool.rst

@@ -266,9 +266,7 @@ discussed here. Run ``west <command> -h`` for detailed help.
   manifest file, such as URL, revision, path, etc. The printed information can
   be controlled using the ``-f`` option.
 
-- ``west manifest --freeze [-o outfile]``: Save a "frozen" representation of
+- ``west manifest``: Manipulates manifest files. See :ref:`west-manifest-cmd`.
-  the current manifest; all ``revision`` fields are converted to SHAs based on
-  the current ``manifest-rev`` branches.
 
 - ``west manifest --validate``: Ensure the current manifest file is
   well-formed. Print information about what's wrong and fail the process in