Move back the purge extension in hgext

hgext/purge.py

@@ -8,7 +8,7 b''
 #
 # To enable the "purge" extension put these lines in your ~/.hgrc:
 #  [extensions]
-#  purge = /path/to/purge.py
+#  hgext.purge =
 #
 # For help on the usage of "hg purge" use:
 #  hg help purge

tests/test-purge

@@ -2,7 +2,7 b''
 
 cat <<EOF >> $HGRCPATH
 [extensions]
-purge=${TESTDIR}/../contrib/purge/purge.py
+hgext.purge=
 EOF
 
 echo % init