Sync move-if-change from Gnulib

This alters move-if-change so that its --version option outputs
the correct copyright date automatically.  One less thing
to update by hand.

scripts/move-if-change

@@ -8,7 +8,7 @@ VERSION='2018-03-07 03:47'; # UTC
 # If you change this file with Emacs, please let the write hook
 # do its job.  Otherwise, update this string manually.
 
-# Copyright (C) 2002-2019 Free Software Foundation, Inc.
+# Copyright (C) 2002-2021 Free Software Foundation, Inc.
 
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -36,9 +36,10 @@ The variable CMPPROG can be used to specify an alternative to 'cmp'.
 
 Report bugs to <bug-gnulib@gnu.org>."
 
+year=`expr "$VERSION" : '\([^-]*\)'`
 version=`expr "$VERSION" : '\([^ ]*\)'`
 version="move-if-change (gnulib) $version
-Copyright (C) 2011 Free Software Foundation, Inc.
+Copyright $year Free Software Foundation, Inc.
 License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
 This is free software: you are free to change and redistribute it.
 There is NO WARRANTY, to the extent permitted by law."