Update the {touch, date} code to use parse_datetime 0.5.0

[sylvestre]

a lot of changes have been made to parse_datetime.
https://github.com/uutils/parse_datetime

The code of touch & date needs to be updated

[sylvestre]

To start, just update Cargo.toml to update the version
and to test:

$ cargo test --features=unix  test_touch 
$ cargo test --features=unix  test_date

[u8sand]

I tackled this and made the following patch which does pass the tests but I'm not quite satisfied.
https://gist.github.com/u8sand/f957ccf502007d068948193660736270

The main problem is that parse_datetime does not distinguish between relative/absolute datetimes, but touch has different behavior for relative/absolute (at least the tests suggest this). I think parse_datetime should be updated to allow you to make this distinction.

Maybe i'll get to it or someone else can pick it up from here, I figured I may as well share what was already done.

[sylvestre]

@philolo1 any suggestion ? :)

[tertsdiepraam]

Nice @u8sand! The idea of the parse_datetime API is that the difference between absolute and relative is built-in. So you give it a reference time to parse from, and if the format is relative it will do the calculations from that date. If it is absolute that reference date will be ignored. So, in theory, it should be as easy as this:

• get the atime and mtime,
• parse the date format twice, once with atime and once mtime as reference,
• use the time that parse_datetime returns.
  If that doesn't work, please let us know, because that would be a bug in parse_datetime!

If there is no reference file passed, then the current datetime should be used as reference.

[u8sand]

@tertsdiepraam you're right, perhaps it's just premature optimization that I hoped to run parse_datetime just once. PR on its way