cp is unable to copy a deep directory

$ ~/.cargo/bin/coreutils
coreutils 0.0.29 (multi-call binary)

Copying very deep directory structure fails:

$ (for i in `seq 1 2000`; do mkdir 1234567890123456789012345678901234567890; cd 1234567890123456789012345678901234567890; done)
 
$ ~/.cargo/bin/coreutils cp -a 1234567890123456789012345678901234567890 2
cp: cannot stat '/home/users/arekm/test/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890/1234567890123456789012345678901234567890': File name too long (os error 36)

cp should be able to walk the structure in a such way to always avoid too long file name lengths and be able to copy such directory.

In gnu coreutils "cp" unfortunately is also lacking in this area and hits "File name too long" but for example "rm" was made better, so it doesn't hit this limit. (uutils coreutils rm has issue with that - #7375 - but that's another story)

Consider this as feature request to change the way "cp" walks while copying directory to be able to copy even such deep structures.

In real life I'm hitting this problem when using rsnapshot for doing backups. It uses "cp -al" to copy structure and that just fails with such paths. So it's not just a theoretical problem.

Start by locating the cp command implementation and its directory-walking path; the issue provides no file or test names. Reproduce the 2,000-level directory example and define done as cp -a, including the cited cp -al backup use case, copying it without a File name too long error.