add note about minicpan mirrors and core-cpan-diff

diff --git a/Porting/release_managers_guide.pod b/Porting/release_managers_guide.pod
index 6e75865..9dac56e 100644 (file)
--- a/Porting/release_managers_guide.pod
+++ b/Porting/release_managers_guide.pod
@@ -199,7 +199,10 @@ to see any inconsistencies between the core and CPAN versions of distros,
 then fix the core, or cajole CPAN authors as appropriate. See also the
 C<-d> and C<-v> options for more detail.  You'll probably want to use the
 C<-c cachedir> option to avoid repeated CPAN downloads and may want to
-use C<-m file:///mirror/path> if you made a local CPAN mirror.
+use C<-m file:///mirror/path> if you made a local CPAN mirror. Note that
+a minicpan mirror won't actually work, but can provide a good first pass
+to quickly get a list of modules which definitely haven't changed, to
+avoid having to download absolutely everything.
 
 To see which core distro versions differ from the current CPAN versions: