Various updates for PEP 643

1. Remove the whitelist of fields allowed to be dynamic.
2. Allow Dynamic outside of source distributions.

Author: pfmoore

source/specifications/core-metadata.rst

@@ -84,26 +84,29 @@ Dynamic (multiple use)
 
 .. versionadded:: 2.2
 
-Only permitted in source distribution (sdist) file metadata.
-
-A string containing the name of another core metadata field. Only the following
-metadata field names may be used as the value of the ``Dynamic`` field.
-
-* ``Platform``
-* ``Supported-Platform``
-* ``Requires-Dist``
-* ``Requires-External``
-* ``Provides-Extra``
-* ``Provides-Dist``
-* ``Obsoletes-Dist``
-
-Unless specified via ``Dynamic``, *all* metadata in a wheel must be identical to
-the metadata of the sdist from which the wheel was built. If a field is named in
-``Dynamic`` in the sdist, then there is no constraint on what value that field
-may have in wheels built from the sdist.
-
-If the sdist metadata version is older than version 2.2, then there are no
-constraints on the metadata of wheels built from that sdist.
+A string containing the name of another core metadata field. The field
+names ``Name`` and ``Version`` may not be specified in this field.
+
+When found in the metadata of a source distribution, the following
+rules apply:
+
+1. If a field is *not* marked as ``Dynamic``, then the value of the field
+   in any wheel built from the sdist MUST match the value in the sdist.
+   If the field is not in the sdist, and not marked as ``Dynamic``, then
+   it MUST NOT be present in the wheel.
+2. If a field is marked as ``Dynamic``, it may contain any valid value in
+   a wheel built from the sdist (including not being present at all).
+
+If the sdist metadata version is older than version 2.2, then all fields should
+be treated as if they were specified with ``Dynamic`` (i.e. there are no special
+restrictions on the metadata of wheels built from the sdist).
+
+In any context other than a source distribution, ``Dynamic`` is for information
+only, and indicates that the field value was calculated at wheel build time,
+and may not be the same as the value in the sdist or in other wheels for the
+project.
+
+Full details of the semantics of ``Dynamic`` are described in :pep:`643`.
 
 
 Platform (multiple use)

source/specifications/source-distribution-format.rst

@@ -13,9 +13,9 @@ documented here.
 There is also the legacy source distribution format, implicitly defined by the
 behaviour of ``distutils`` module in the standard library, when executing
 ``setup.py sdist``. This document does not attempt to standardise this format,
-except to note that if a legacy sdist contains a ``PKG-INFO`` file holding
-metadata version 2.2 or later, that sdist MUST follow the rules for sdists
-defined by the metadata specification.
+except to note that if a legacy source distribution contains a ``PKG-INFO``
+file holding metadata version 2.2 or later, then it MUST follow the rules
+applicable to source distributions defined in the metadata specification.
 
 Source distributions are also known as *sdists* for short.
 
@@ -33,7 +33,7 @@ in the metadata contained in the file.
 Source distribution file format
 ===============================
 
-A .tar.gz source distribution (sdist) contains a single top-level directory
+A ``.tar.gz`` source distribution (sdist) contains a single top-level directory
 called ``{name}-{version}`` (e.g. ``foo-1.0``), containing the source files of
 the package. The name and version MUST match the metadata stored in the file.
 This directory must also contain a ``pyproject.toml`` in the format defined in