ls: don't show . and .. on orphaned directories

[zveihander]

Fixes #12968

When a directory is deleted and replaced by another file system object while a process still has it open as its working directory, runing ls with the -a flag from the orphaned directory still shows . and ... the GNU ls does not show anything in this case.

The dots were being added unconditionally whenever -a was used, without checking whether the directory is still in the filesystem tree.

It now checks whether the directory is still reachable from the parent by comparing inode and device against the parent's stats before it adds the dots.

[sylvestre]

please add a test to make sure we don't regress, thanks

[github-actions]

Binary size comparison:

Individual binary size comparison VS main (threshold: >=5% AND >=4 KB).

Total size of compared binaries: 148.97 MB (-132 KB, -0.09%)

Significant per-binary changes:
  [           1.10 MB ->    1.18 MB  (+76 KB, +6.74%)
  test        1.10 MB ->    1.18 MB  (+76 KB, +6.74%)
  install     1.25 MB ->    1.32 MB  (+72 KB, +5.62%)
  mkdir       1.10 MB ->    1.17 MB  (+72 KB, +6.38%)
  mkfifo      1.09 MB ->    1.16 MB  (+72 KB, +6.45%)
  mknod       1.10 MB ->    1.17 MB  (+72 KB, +6.41%)
  chmod       1.15 MB ->    1.22 MB  (+68 KB, +5.76%)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/timeout/timeout-group (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/follow-name (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/cat/splice is no longer failing!
Congrats! The gnu test tests/cut/mb-non-utf8 is no longer failing!
Congrats! The gnu test tests/ls/stat-free-symlinks is no longer failing!
Congrats! The gnu test tests/mv/dir2dir is no longer failing!
Congrats! The gnu test tests/mv/mv-exchange is no longer failing!
Congrats! The gnu test tests/nl/multibyte is no longer failing!
Congrats! The gnu test tests/od/od-j is no longer failing!
Note: The gnu test tests/printf/printf-surprise is now being skipped but was previously passing.
Congrats! The gnu test tests/dd/no-allocate is now passing!
Note: The gnu test tests/misc/write-errors was skipped on 'main' but is now failing.

[codspeed-hq]

Merging this PR will degrade performance by 53.8%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 1 improved benchmark
❌ 4 regressed benchmarks
✅ 348 untouched benchmarks
⏩ 50 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	ls_recursive_long_all_wide_tree[(15000, 1500)]	231.4 ms	7,723.9 ms	-97%
❌	Simulation	ls_recursive_long_all_balanced_tree[(6, 4, 15)]	284.4 ms	335.2 ms	-15.16%
❌	Simulation	ls_recursive_long_all_mixed_tree	5.6 ms	6.5 ms	-13.82%
❌	Simulation	ls_recursive_long_all_deep_tree[(100, 4)]	6.3 ms	6.8 ms	-7.43%
⚡	Simulation	complex_relative_date	330.6 µs	318.6 µs	+3.77%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing zveihander:ls-orphan-directory-dots (c2e3bc7) with main (a56bff2)}

Footnotes

1. 50 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩