doc: NEWS: explain _why_ copy_file_range() is used

* NEWS: Mention why we're making the change in behavior in cat(1).

diff --git a/NEWS b/NEWS
index 757abee1543b7d2fe7a16df665ebf1ddd82a95a6..ebcd5cb2f5072cb5b0e7396c53b0d33fbf04d07c 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -35,7 +35,8 @@ GNU coreutils NEWS                                    -*- outline -*-
 ** Changes in behavior
 
   cat now uses the copy_file_range syscall if available, when doing
-  simple copies between regular files.
+  simple copies between regular files.  This may be more efficient, by avoiding
+  user space copies, and possibly employing copy offloading or reflinking.
 
   date +'%-N' now suppresses excess trailing digits, instead of always
   padding them with zeros to 9 digits.  It uses clock_getres and