Mark tag_svn_revision as deprecated. Ref #619.

CHANGES.rst

@@ -2,6 +2,12 @@
 CHANGES
 =======
 
+v23.1.0
+-------
+
+* #619: Deprecated ``tag_svn_revision`` distribution
+  option.
+
 v23.0.0
 -------
 

setuptools/command/egg_info.py

@@ -199,6 +199,10 @@ class egg_info(Command):
         if self.tag_build:
             version += self.tag_build
         if self.tag_svn_revision:
+            warnings.warn(
+                "tag_svn_revision is deprecated and will not be honored "
+                "in a future release"
+            )
             version += '-r%s' % self.get_svn_revision()
         if self.tag_date:
             version += time.strftime("-%Y%m%d")