File::lock docs don't make clear they are cross-process

[Mark-Simulacrum]

Location (URL)

https://doc.rust-lang.org/nightly/std/fs/struct.File.html#method.lock

Summary

The current documentation doesn't mention "process" in the lock/lock_shared methods at all. The only clue without either prior knowledge or reading the man pages that these methods do work across processes is this line:

This acquires an exclusive lock; no other file handle to this file may acquire another lock.

But this requires understanding what relation a file handle has to the file, etc. We should make the use for these methods clearer to readers.

[Mark-Simulacrum]

I'd be happy to review a PR suggesting concrete wording here. It likely makes sense to either have a slightly longer section in one method and cross-link it across {try_,}lock{_shared,}, or copy/paste the same sentence across all N methods.

[TKanX]

@rustbot claim