Added obsolete fields: requires, provides and obsoletes

closes: #1107

Author: venthur

source/specifications/core-metadata.rst

@@ -755,6 +755,92 @@ Examples::
     Obsoletes-Dist: OtherProject (<3.0)
     Obsoletes-Dist: Foo; os_name == "posix"
 
+
+Deprecated Fields
+=================
+
+Requires
+--------
+
+.. versionadded:: 1.1
+.. deprecated:: 1.2
+   in favour of ``Requires-Dist``
+
+Each entry contains a string describing some other module or package required
+by this package.
+
+The format of a requirement string is identical to that of a module or package
+name usable with the ‘import’ statement, optionally followed by a version
+declaration within parentheses.
+
+A version declaration is a series of conditional operators and version numbers,
+separated by commas. Conditional operators must be one of "<", ">"', "<=",
+">=", "==", and "!=". Version numbers must be in the format accepted by the
+``distutils.version.StrictVersion`` class: two or three dot-separated numeric
+components, with an optional "pre-release" tag on the end consisting of the
+letter 'a' or 'b' followed by a number. Example version numbers are "1.0",
+"2.3a2", "1.3.99",
+
+Any number of conditional operators can be specified, e.g. the string ">1.0,
+!=1.3.4, <2.0" is a legal version declaration.
+
+All of the following are possible requirement strings: "rfc822", "zlib
+(>=1.1.4)", "zope".
+
+There’s no canonical list of what strings should be used; the Python community
+is left to choose its own standards.
+
+Examples::
+
+    Requires: re
+    Requires: sys
+    Requires: zlib
+    Requires: xml.parsers.expat (>1.0)
+    Requires: psycopg
+
+
+Provides
+--------
+
+.. versionadded:: 1.1
+.. deprecated:: 1.2
+   in favour of ``Provides-Dist``
+
+Each entry contains a string describing a package or module that will be
+provided by this package once it is installed. These strings should match the
+ones used in Requirements fields. A version declaration may be supplied
+(without a comparison operator); the package’s version number will be implied
+if none is specified.
+
+Examples::
+
+    Provides: xml
+    Provides: xml.utils
+    Provides: xml.utils.iso8601
+    Provides: xml.dom
+    Provides: xmltools (1.3)
+
+
+Obsoletes
+---------
+
+.. versionadded:: 1.1
+.. deprecated:: 1.2
+   in favour of ``Obsoletes-Dist``
+
+Each entry contains a string describing a package or module that this package
+renders obsolete, meaning that the two packages should not be installed at the
+same time. Version declarations can be supplied.
+
+The most common use of this field will be in case a package name changes, e.g.
+Gorgon 2.3 gets subsumed into Torqued Python 1.0. When you install Torqued
+Python, the Gorgon package should be removed.
+
+Example::
+
+    Obsoletes: Gorgon
+
+
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