[Reproducible-builds] [Debian Wiki] Update of "ReproducibleBuilds/TimestampsProposal" by BenBoeckel

[Daniel Kahn Gillmor]

On Wed 2015-09-16 21:19:59 -0400, Debian Wiki wrote:
> Dear Wiki user,
>
> You have subscribed to a wiki page or wiki category on "Debian Wiki" for change notification.
>
> The "ReproducibleBuilds/TimestampsProposal" page has been changed by BenBoeckel:
> https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal?action=diff&rev1=44&rev2=45
>
> Comment:
> CMake: update example to use lower-case command names, use $ENV{SOURCE_DATE_EPOCH}, fix argument quoting, strip trailing whitespace, and formatting cleanup so it is easier to read
>
>   
>   {{{
>   if (DEFINED ENV{SOURCE_DATE_EPOCH})
> -   EXECUTE_PROCESS(COMMAND "date" "-u" "-d @${SOURCE_DATE_EPOCH}" "+%d/%m/%Y" OUTPUT_VARIABLE BUILD_DATE)
> +   execute_process(
> +     COMMAND "date" "-u" "-d" "@$ENV{SOURCE_DATE_EPOCH}" "+%d/%m/%Y"
> +     OUTPUT_VARIABLE BUILD_DATE
> +     OUTPUT_STRIP_TRAILING_WHITESPACE)
> - else()
> + else ()
> -   EXECUTE_PROCESS(COMMAND "date" "+%d/%m/%Y" OUTPUT_VARIABLE BUILD_DATE)
> +   execute_process(
> +     COMMAND "date" "+%d/%m/%Y"
> +     OUTPUT_VARIABLE BUILD_DATE
> +     OUTPUT_STRIP_TRAILING_WHITESPACE)
> - endif()
> + endif ()
>   }}}
>   
>   ''The above will work only with GNU date. See POSIX shell example on how to support BSD date.''

Is there a reason above that this example code to translate from
SOURCE_DATE_EPOCH to a build date doesn't produce ISO-8601-compliant
date strings in the BUILD_DATE variable?

I'm happy to replace "+%d/%m/%Y" with "+%Y-%m-%d", but i don't know much
about cmake and don't want to get in an edit war about this.

fwiw, "%d/%m/%Y" may look sane to most people around the world, but it
has the following disadvantages over ISO-8601:

 0) lexicographically-sorted dates are not chronologically-sorted

 1) the US typically uses "+%m/%d/%Y" (which is insane, granted) which
    means that 06/09/2015 is easily interpretable as June 9th as well as
    September 6th.

    --dkg