rbd docs: document cp versus deep cp

I found that the difference between "rbd cp" and "rbd deep cp",
i.e. what "deep" means in this context, is documented only in
the mailing list archive and in the Mimic reelase notes.

Let's make the difference explicit in the manpage and in rbd --help.

Signed-off-by: Jan "Yenya" Kasprzak <kas@fi.muni.cz>

doc/man/8/rbd.rst

@@ -237,6 +237,8 @@ Commands
 :command:`cp` (*src-image-spec* | *src-snap-spec*) *dest-image-spec*
   Copy the content of a src-image into the newly created dest-image.
   dest-image will have the same size, object size, and image format as src-image.
+  Note: snapshots are not copied, use `deep cp` command to include
+  snapshots.
 
 :command:`create` (-s | --size *size-in-M/G/T*) [--image-format *format-id*] [--object-size *size-in-B/K/M*] [--stripe-unit *size-in-B/K/M* --stripe-count *num*] [--thick-provision] [--no-progress] [--image-feature *feature-name*]... [--image-shared] *image-spec*
   Will create a new rbd image. You must also specify the size via --size.  The

src/test/cli/rbd/help.t

@@ -26,7 +26,7 @@
       config pool set                   Set a pool-level configuration override.
       copy (cp)                         Copy src image to dest.
       create                            Create an empty image.
-      deep copy (deep cp)               Deep copy src image to dest.
+      deep copy (deep cp)               Deep copy (including snapshots) src image to dest.
       device list (showmapped)          List mapped rbd images.
       device map (map)                  Map an image to a block device.
       device unmap (unmap)              Unmap a rbd device.
@@ -531,7 +531,7 @@
                        [--no-progress] 
                        <source-image-or-snap-spec> <dest-image-spec> 
   
-  Deep copy src image to dest.
+  Deep copy (including snapshots) src image to dest.
   
   Positional arguments
     <source-image-or-snap-spec>  source image or snapshot specification

src/tools/rbd/action/Copy.cc

@@ -187,7 +187,7 @@ int execute_deep(const po::variables_map &vm,
 }
 
 Shell::Action action_deep(
-  {"deep", "copy"}, {"deep", "cp"}, "Deep copy src image to dest.",
+  {"deep", "copy"}, {"deep", "cp"}, "Deep copy (including snapshots) src image to dest.",
   at::get_long_features_help(), &get_arguments_deep, &execute_deep);
 
 } // namespace copy