cp: Fix broken symlinks to parent-dir

[luigieli]

According to the GNU cp official documentation, a symlink is only created if all source paths are absolute, unless the destination files are in the current directory.

This fix solves this GNU cp incompatibility by:

• Adding verifications when handling symlinks, to ensure that a symlink with relative path are only created if the destination is within the current directory.
• Adding unit tests to cover this modifications, and ensure the behavior is correctly align with GNU documentation.

Fixes #6385.

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/timeout/timeout. tests/timeout/timeout is passing on 'main'. Maybe you have to rebase?
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/timeout/timeout is no longer failing!

[BenWiederhake]

Looks good! The new feature is in a sensible place, the tests cover both the positive and the negative case, awesome.

I can't merge this yet because GitHub says there are conflicts (even though they actually are only trivial conflicts), and also because one of the tests is broken (see below).

[BenWiederhake]

This fails on Windows, because there it generates the error message with a backslash.

[luigieli]

Oh I see! Really appreciate the review. About the broken test in Windows, I think stderr_contains() can be used instead of stderr_is() to address this, I'm going to try it to solve this compatibility issue with Windows, along with the conflicts.

[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]

CI still says the new test is broken, and at first glance the error message seems reasonable.

[luigieli]

CI still says the new test is broken, and at first glance the error message seems reasonable.

The error caused by the backslash in Windows was solved, but there are still 4 tests failing only in Windows, I'll try to figure out why of those failures.

[sylvestre]

@luigieli do you have an update on this? thanks

[luigieli]

@sylvestre Sorry for disappearing, I was really busy due to college, so I couldn't exhaust my debugging options and the bugs in Windows are still persisting. Would it be okay if I bring you a more detailed update on this by Monday?

[luigieli]

As I promised, I tried to debug the Windows errors. I used a virtual machine with Windows 11 in it to try reproducing the errors, but it was unsuccessful, for some reason when I cargo test in the VM, almost no tests were made, after activating developer mode in Windows, I could indeed run the tests, but all of them passed, even the ones that are failing in the CI. I'm not so used to windows, so I would appreciate any ideas on how to proceed.

[sylvestre]

Fails on Windows on:

--- TRY 3 STDERR:        coreutils::tests test_cp::test_symlink_mode_overwrite ---
thread 'test_cp::test_symlink_mode_overwrite' panicked at tests\by-util\test_cp.rs:5908:14:
assertion failed: `(left == right)`

Diff < left / right > :
<cp: .\t: can make relative symbolic links only in current directory
<cp: .\t: can make relative symbolic links only in current directory
>cp: will not overwrite just-created '.\t' with 'b\t'
 


stack backtrace:
   0: std::panicking::begin_panic_handler
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/std\src\panicking.rs:662
   1: core::panicking::panic_fmt
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\panicking.rs:74
   2: tests::common::util::CmdResult::stderr_is<ref$<str$> >
             at .\tests\common\util.rs:586
   3: tests::common::util::CmdResult::stderr_only<ref$<str$> >
             at .\tests\common\util.rs:642
   4: tests::test_cp::test_symlink_mode_overwrite
             at .\tests\by-util\test_cp.rs:5903
   5: tests::test_cp::test_symlink_mode_overwrite::closure$0
             at .\tests\by-util\test_cp.rs:5885
   6: core::ops::function::FnOnce::call_once<tests::test_cp::test_symlink_mode_overwrite::closure_env$0,tuple$<> >
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library\core\src\ops\function.rs:250
   7: core::ops::function::FnOnce::call_once
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14\library/core\src\ops\function.rs:250
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[sylvestre]

@luigieli it is still marked as draft, are you still working on it? thanks

[luigieli]

@sylvestre Yes, I'm still trying to debug and solve the fails on Windows. I'll bring news as soon as possible. Appreciate the waiting. Thanks!