Add explanation of what happens for wp role reset (#58)

README.md

@@ -187,6 +187,12 @@ Resets any default role to default capabilities.
 wp role reset [<role-key>...] [--all]
 ~~~
 
+Uses WordPress' `populate_roles()` function to put one or more
+roles back into the state they were at in the a fresh
+WordPress install. Removes any capabilities that were added,
+and restores any capabilities that were removed. Custom roles
+are not affected.
+
 **OPTIONS**
 
 	[<role-key>...]
@@ -197,9 +203,17 @@ wp role reset [<role-key>...] [--all]
 
 **EXAMPLES**
 
-    # Reset role.
+    # Reset three roles.
     $ wp role reset administrator author contributor
-    Success: Reset 1/3 roles.
+    Restored 1 capability to and removed 0 capabilities from 'administrator' role.
+    No changes necessary for 'author' role.
+    No changes necessary for 'contributor' role.
+    Success: 1 of 3 roles reset.
+
+    # Reset a custom role.
+    $ wp role reset custom_role
+    Custom role 'custom_role' not affected.
+    Error: Must specify a default role to reset.
 
     # Reset all default roles.
     $ wp role reset --all

src/Role_Command.php

@@ -245,6 +245,12 @@ public function delete( $args ) {
 	/**
 	 * Resets any default role to default capabilities.
 	 *
+	 * Uses WordPress' `populate_roles()` function to put one or more
+	 * roles back into the state they were at in the a fresh
+	 * WordPress install. Removes any capabilities that were added,
+	 * and restores any capabilities that were removed. Custom roles
+	 * are not affected.
+	 *
 	 * ## OPTIONS
 	 *
 	 * [<role-key>...]
@@ -255,9 +261,17 @@ public function delete( $args ) {
 	 *
 	 * ## EXAMPLES
 	 *
-	 *     # Reset role.
+	 *     # Reset three roles.
 	 *     $ wp role reset administrator author contributor
-	 *     Success: Reset 1/3 roles.
+	 *     Restored 1 capability to and removed 0 capabilities from 'administrator' role.
+	 *     No changes necessary for 'author' role.
+	 *     No changes necessary for 'contributor' role.
+	 *     Success: 1 of 3 roles reset.
+	 *
+	 *     # Reset a custom role.
+	 *     $ wp role reset custom_role
+	 *     Custom role 'custom_role' not affected.
+	 *     Error: Must specify a default role to reset.
 	 *
 	 *     # Reset all default roles.
 	 *     $ wp role reset --all