Implement fd_filestat_set_times using the filetime crate.

[marmistrz]

In the future we could consider using filetime to replace systemtime_to_timestamp from #42.

[marmistrz]

I rebased the change upon the new revision of #46.

[sunfishcode]

This looks good to me. In particular, the interpretation of MTIM vs MTIM_NOW and so on looks reasonable. It looks compatible with WASI libc, and in general rejecting unimportant variations in usage will make things more consistent.

Would you mind adding a test for this to wasi-misc-tests?

[marmistrz]

I'll add a test.

Can we change the spec to be explicit about the MTIM vs MTIM_NOW interpretation and close #53 (I probably should've raised the issue against wasmtime, not wasi-common)

[sunfishcode]

Yeah. Actually, the best place to file #53 is the WASI issue tracker, tagged with wasi-filesystem.

[sunfishcode]

Sounds good. And this just needs a few conflicts resolved before we can merge it.

[kubkon]

@marmistrz could you fix conflicts please?

[marmistrz]

This still needs some work to pass the new test.

[kubkon]

It's really interesting that it fails on *nixes and not Windows :-)

[marmistrz]

Because I haven't enabled them yet on Windows :P

[kubkon]

Haha, touche! Totally forgot about that! :-D Lemme know if you need any help with debugging or whatnot!

[marmistrz]

The reason why CI on Mac fails is that on Mac filetime uses utimes and not utimensat. The former has microsecond precision, the latter - nanosecond. https://github.com/alexcrichton/filetime/blob/master/src/unix/mod.rs#L6-L23

@alexcrichton is there any reason why we can't use utimensat on Mac? The previous implementation in wasi-common used utimensat and passed the CI. utimensat should be available starting from MacOS 10.13.

[kubkon]

@marmistrz do you want me try filetime out on macos with utimensat used instead of utimes? If it passes, we could submit a PR with a fix to @alexcrichton's repo.

[kubkon]

@alexcrichton, together with @marmistrz we've worked out that @marmistrz's changes build and test out fine with alexcrichton/filetime#43 patch applied. Could you have a look and let me know what changes should be made to that PR so that we could merge it in, etc.?