cp -n prints warning on stderr

[Nick Rosbrook]

With coreutils, cp -n will start printing a warning on stderr:

  cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead

See the debian bug for some more context: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1058752

This change may cause issues in other packages autopkgtest (given the stderr output) or elsewhere, so this bug is used to track such cases.

[Nick Rosbrook (enr0n)]

This affects initramfs-tools autopkgtest[1]:

4856s autopkgtest [23:01:25]: test qemu-net: -----------------------]
4857s autopkgtest [23:01:26]: test qemu-net: - - - - - - - - - - results - - - - - - - - - -
4857s qemu-net FAIL stderr: cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s autopkgtest [23:01:26]: test qemu-net: - - - - - - - - - - stderr - - - - - - - - - -
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s cp: warning: behavior of -n is non-portable and may change in future; use --update=none instead
4857s c...

[Nick Rosbrook (enr0n)]

The usage of cp -n that causes this is actually in /usr/share/initramfs-tools/hooks/klibc-utils, which is already fixed in -proposed: https://launchpad.net/ubuntu/+source/klibc/2.0.13-4.