Re: suggested feautre: "date --debug" - print date parsing diagnostics

[Pádraig Brady]

On 23/01/16 06:29, Assaf Gordon wrote:
> Attached yet another improvement, this time supporting detailed timezone 
> information.

Yes it's definitely worth debugging the TZ stuff since
there are multiple ways to set it.

> Examples below, all examples run on a computer with default timezone of 
> EST=-05:00 .
> 
> Comments welcomed,

General notes on patch.

Spellings:
  s/debug_print_relateive_time/debug_print_relative/ in gnulib commit msg
  s/relatie/relative/
  s/eigth/eight/
  s/unambigious/unambiguous/
  s/timezome/timezone/
  s/modfied/modified/

Avoid -Werror=strict-prototypes
  s/get_effective_timezone ()/get_effective_timezone (void)/

parse_datetime module needs to declare dependency on timegm module

prefer fn () to fn() calls in various places

%zu is not supported. See for example:
  http://git.sv.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=v8.23-75-g7d1fe88

> Explaining the 'bug' ( http://debbugs.gnu.org/22439 ) now becomes:
> ===
> $ ./src/date --debug -d '@0' +%X
> date: parsed timespec part: timespec=0 seconds

  s/timespec/number of seconds/
  s/timepec=//

> date: warning: default input timezone: -05:00

  "warning" is a bit strong.
  Note -u overrides TZ in the env which is not obvious, so maybe
  we could say what input timezone is and where it came from?
  This would also remove the need for a separate
  "timezone modified by explicit TZ value" line. I.e.:

  date: input timezone: ±HH:MM (set from $where)

    $where can be:
      --utc option
      TZ=... in date string (to distinguish from TZ in env)
      TZ=... environment value (good to print value as may be inherited)
      system default

> date: final epoch-seconds: 0.000000000
> date: final date: '(Y-M-D) 1970-01-01 00:00:00' UTC
> date: final date: '(Y-M-D) 1969-12-31 19:00:00' (local TZ=-05:00)
> 19:00:00

thanks!
Pádraig