cp: Added overwrite detection for existing symlinks

[AnirbanHalder654322]

Fixes #6265

[BenWiederhake]

Thanks for tackling this issue!

By slightly changing the test setup, you (accidentally?) created another interesting test case, please keep it! :D

EDIT: Regarding the clippy failure: I'm afraid the sheer amount of "state" that is passed between the various copy-functions means that this really should be changed to a struct, perhaps?

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cp/link-deref. tests/cp/link-deref is passing on 'main'. Maybe you have to rebase?
Congrats! The gnu test tests/cksum/cksum-a is no longer failing!
Congrats! The gnu test tests/cksum/sm3sum is no longer failing!

[AnirbanHalder654322]

The state can be refactored and encapsulated within a struct . Perhaps that can be addressed in a future PR .

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)

[BenWiederhake]

Mostly just questions, there's probably not much to do anymore.

Also, can I convince you to remove #[allow(clippy::too_many_arguments)] in your next PR?

[BenWiederhake]

LGTM! We're still bad at handling symlinks, but this is a step in the right direction. Yay! :)