cp,mv: skipping due to -u is success, not failure

This reverts the previous change, so that when a file
is skipped due to -u, this is not considered a failure.
* doc/coreutils.texi: Document this.
* src/copy.c (copy_internal): If --update says to skip,
treat this as success instead of failure.
* tests/mv/update.sh, tests/cp/slink-2-slink.sh:
Revert previous change, to match reverted behavior.

doc/coreutils.texi

@@ -9191,8 +9191,8 @@ results in an error message on systems that do not support symbolic links.
 @opindex --update
 @cindex newer files, copying only
 Do not copy a non-directory that has an existing destination with the
-same or newer modification timestamp; silently fail instead.
-If timestamps are being preserved,
+same or newer modification timestamp; instead, silently skip the file
+without failing.  If timestamps are being preserved,
 the comparison is to the source timestamp truncated to the
 resolutions of the destination file system and of the system calls
 used to update timestamps; this avoids duplicate work if several
@@ -10124,7 +10124,8 @@ fail with a diagnostic instead of copying and then removing the file.
 @opindex --update
 @cindex newer files, moving only
 Do not move a non-directory that has an existing destination with the
-same or newer modification timestamp; silently fail instead.
+same or newer modification timestamp;
+instead, silently skip the file without failing.
 If the move is across file system boundaries, the comparison is to the
 source timestamp truncated to the resolutions of the destination file
 system and of the system calls used to update timestamps; this avoids

src/copy.c

@@ -2197,7 +2197,7 @@ copy_internal (char const *src_name, char const *dst_name,
                         }
                     }
 
-                  return false;
+                  return true;
                 }
             }
 

tests/cp/slink-2-slink.sh

@@ -26,7 +26,7 @@ ln -s file b || framework_failure_
 ln -s no-such-file c || framework_failure_
 ln -s no-such-file d || framework_failure_
 
-returns_ 1 cp --update --no-dereference a b || fail=1
-returns_ 1 cp --update --no-dereference c d || fail=1
+cp --update --no-dereference a b || fail=1
+cp --update --no-dereference c d || fail=1
 
 Exit $fail

tests/mv/update.sh

@@ -29,8 +29,7 @@ for interactive in '' -i; do
     # This is a no-op, with no prompt.
     # With coreutils-6.9 and earlier, using --update with -i would
     # mistakenly elicit a prompt.
-    returns_ 1 $cp_or_mv $interactive --update old new </dev/null >out 2>&1 ||
-      fail=1
+    $cp_or_mv $interactive --update old new < /dev/null > out 2>&1 || fail=1
     compare /dev/null out || fail=1
     case "$(cat new)" in new) ;; *) fail=1 ;; esac
     case "$(cat old)" in old) ;; *) fail=1 ;; esac