Add info to "pin rm" help about how to tell if a pin is indirectly pi…

…nned.

Addresses issue #7440

core/commands/pin/pin.go

@@ -204,6 +204,14 @@ var rmPinCmd = &cmds.Command{
 		ShortDescription: `
 Removes the pin from the given object allowing it to be garbage
 collected if needed. (By default, recursively. Use -r=false for direct pins.)
+`,
+		LongDescription: `
+Removes the pin from the given object allowing it to be garbage
+collected if needed. (By default, recursively. Use -r=false for direct pins.)
+
+A pin may not be removed because the specified object is not pinned or pinned
+indirectly. To determine if the object is pinned indirectly, use the command:
+ipfs pin ls -t indirect <cid>
 `,
 	},