Re: [PATCH v2] date.c: allow ISO 8601 reduced precision times

> ISO 8601 permits "reduced precision" time representations to omit the
> seconds value or both the minutes and the seconds values.  The
> abbreviate times could look like 17:45 or 1745 to omit the seconds,
> or simply as 17 to omit both the minutes and the seconds.
>
> parse_date_basic accepts the 17:45 format but it rejects the other two.
> Change it to accept 4-digit and 2-digit time values when they follow a
> recognized date and a 'T'.
>
> Before this change:
>
> $ TZ=UTC test-tool date approxidate 2022-12-13T23:00 2022-12-13T2300 2022-12-13T23
> 2022-12-13T23:00 -> 2022-12-13 23:00:00 +0000
> 2022-12-13T2300 -> 2022-12-13 23:54:13 +0000
> 2022-12-13T23 -> 2022-12-13 23:54:13 +0000
>
> After this change:
>
> $ TZ=UTC helper/test-tool date approxidate 2022-12-13T23:00 2022-12-13T2300 2022-12-13T23
> 2022-12-13T23:00 -> 2022-12-13 23:00:00 +0000
> 2022-12-13T2300 -> 2022-12-13 23:00:00 +0000
> 2022-12-13T23 -> 2022-12-13 23:00:00 +0000
>
> Note: ISO 8601 also allows reduced precision date strings such as
> "2022-12" and "2022". This patch does not attempt to address these.
>
> Reported-by: Pat LaVarre <plavarre@purestorage.com>
> Signed-off-by: Phil Hord <phil.hord@gmail.com>
> Signed-off-by: Đoàn Trần Công Danh <congdanhqx@gmail.com>
> ---
>
> Since this is a complete re-implementation from Phil Hord's version.
> I'm reassigning the author to me.
>
> This version change the implementation to only treat the string as ISO8601 if
> a 'T' existed and date has been parsed. I also added a test for parsing
> RFC-822, which Hord accidentally broke.
>
> The commit message has been changed:
> * The example has been changed to be independent from local timezone
> * Remove the mention of adding test-cases, since it's obviously necessary.