cp: fix metadata handling on WASI

[DePasqualeOrg]

Correcting cp metadata handling on WASI requires extensive changes. I’m offering this as a possible reference implementation. It was developed over multiple rounds of review with Codex, and I don’t claim to fully understand everything. I’ll maintain this as a private patch for my own use until the issues are addressed here.

Changes:

• Timestamp preservation for files, symlinks, and recursive directories
• Pre---progress timestamp capture and stale-snapshot checks
• Correct --update skip behavior, including recursive copies
• Optional metadata error handling on WASI
• No-follow source safety on WASI

[codspeed-hq]

Merging this PR will degrade performance by 7.37%

❌ 5 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	cp_recursive_deep_tree[(120, 4)]	25.4 ms	27.8 ms	-8.55%
❌	Simulation	cp_recursive_balanced_tree[(5, 4, 10)]	150.4 ms	163.6 ms	-8.1%
❌	Simulation	cp_preserve_metadata[(5, 4, 10)]	164.9 ms	178.1 ms	-7.43%
❌	Simulation	cp_archive_balanced_tree[(5, 4, 10)]	176.6 ms	189 ms	-6.54%
❌	Simulation	cp_recursive_wide_tree[(6000, 800)]	388.4 ms	414 ms	-6.18%

Tip

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

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_{Comparing DePasqualeOrg:cp-wasi-file-symlink-timestamps (51b913a) 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. ↩

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/cp/preserve-link. tests/cp/preserve-link is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/symlink (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/tail-n0f (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/date/date-locale-hour (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/chmod/only-op is no longer failing!
Congrats! The gnu test tests/cp/preserve-mode is no longer failing!
Congrats! The gnu test tests/cut/mb-non-utf8 is no longer failing!
Congrats! The gnu test tests/du/files0-from is no longer failing!
Congrats! The gnu test tests/expand/mb is no longer failing!
Congrats! The gnu test tests/install/install-C is no longer failing!
Congrats! The gnu test tests/ls/quoting-utf8 is no longer failing!
Congrats! The gnu test tests/ls/stat-free-symlinks is no longer failing!
Congrats! The gnu test tests/misc/selinux 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!
Congrats! The gnu test tests/split/split-io-err is no longer failing!
Congrats! The gnu test tests/unexpand/mb is no longer failing!
Note: The gnu test tests/mv/i-3 is now being skipped but was previously passing.
Note: The gnu test tests/stty/bad-speed is now being skipped but was previously passing.
Note: The gnu test tests/stty/stty is now being skipped but was previously passing.
Note: The gnu test tests/stty/stty-invalid is now being skipped but was previously passing.
Note: The gnu test tests/stty/stty-pairs is now being skipped but was previously passing.
Note: The gnu test tests/stty/stty-row-col is now being skipped but was previously passing.
Skip an intermittent issue tests/pr/bounded-memory (was skipped on 'main', now failing)