Document Linux kernel handoff in std::io::copy and std::fs::copy

[sourcefrog]

No description provided.

[rust-highfive]

r? @dtolnay

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[dtolnay]

I agree that there should be some indication here that these descriptions fall under the set of caveats explained in std::io's "Platform-specific behavior" documentation.

Either like this:

rust/library/std/src/env.rs

Lines 28 to 31 in ee915c3

	/// This function [currently] corresponds to the `getcwd` function on Unix
	/// and the `GetCurrentDirectoryW` function on Windows.
	///
	/// [currently]: crate::io#platform-specific-behavior

or like this:

rust/library/std/src/fs.rs

Lines 545 to 549 in ee915c3

	/// This function currently corresponds to the `fchmod` function on Unix and
	/// the `SetFileInformationByHandle` function on Windows. Note that, this
	/// [may change in the future][changes].
	///
	/// [changes]: io#platform-specific-behavior

[sourcefrog]

OK will do.

[sourcefrog]

Done, please take another look.

r? @dtolnay

[dtolnay]

Thanks!

[dtolnay]

@bors r+ rollup

[bors]

📌 Commit cfee2ed has been approved by dtolnay