mv: support moving folder containing symlinks to different filesystem

[yuankunzhang]

Closes #8586.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/misc/stdbuf (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/stdbuf (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[codspeed-hq]

CodSpeed Performance Report

Merging #8605 will not alter performance

_{Comparing yuankunzhang:mv-folder-containing-symlinks-across-fs (a01ee76) with main (ee39b35)}

Summary

✅ 126 untouched
⏩ 6 skipped¹

Footnotes

1. 6 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:

Skip an intermittent issue tests/tail/overlay-headers (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/overlay-headers (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Congrats! The gnu test tests/cksum/cksum-base64-untagged is no longer failing!

[oech3]

Should we share codebase with cp -a instead?
It should fix #9458 automatically

[github-actions]

GNU testsuite comparison:

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

[oech3]

Would you merge this at fix 1 bug at a monent? sudo test issue is traced at different PR and difficult to fix at here.

[oech3]

Would you merge this?

[oech3]

@yuankunzhang @ChrisDryden Would you test mkdir /tmp/{a,b}; unshare -rm bash -c "mount -t tmpfs tmpfs /tmp/a && mount -t tmpfs tmpfs /tmp/b && mkdir -p /tmp/a/d && ln -sv miss /tmp/a/d/dang && mv -v /tmp/a/d /tmp/b" without sudo?