pkg/registries: add a retiring note

The registries package should be retired.  It was introduced as an
easier to use wrapper around c/image `sysregistries` which has been
replaced by `sysregistriesv2` a long while ago.

Users should either use the `sysregistriesv2` package directly or, even
better, we cache the config in libpod's image runtime to prevent
redundant (and ~expensive) parsing of the registries.conf files.

For now, just add a note in hope we'll not forgert about it when we find
time in the future.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

pkg/registries/registries.go

@@ -1,5 +1,10 @@
 package registries
 
+// TODO: this package should not exist anymore.  Users should either use
+// c/image's `sysregistriesv2` package directly OR, even better, we cache a
+// config in libpod's image runtime so we don't need to parse the
+// registries.conf files redundantly.
+
 import (
 	"os"
 	"path/filepath"