readlink: traverse symlinks before resolving ..

[bdrung]

The readlink command from GNU coreutils and the one from uutil coreutils behave differently in case the path contains symlinks and ... GNU readlink traverses symlinks first, but uutils resolves .. first.

Example from Ubuntu 25.10 (questing):

$ gnureadlink -f /sys/class/block/nvme0n1p1/..
/sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/nvme/nvme0/nvme0n1
$ /usr/lib/cargo/bin/coreutils/readlink -f /sys/class/block/nvme0n1p1/..
/sys/class/block

This breaks dracut (see also dracut-ng/dracut#1776).

Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/rust-coreutils/+bug/2134496

[Leviticoh]

this looks like it can be fixed by using ResolveMode::Physical instead of ResolveMode::Logical when using canonicalize,

i'm not sure, was there a specific reason for using Logical? @jaggededgedjustice