bug#51609: version.texi UPDATED field does not account for timezone; can cause unnecessary documentation rebuilds, which could fail

[Karl Berry]

Hi Ryan - thanks for the report. In Automake, those version.texi
variables are updated by the auxiliary script mdate-sh. In Automake
1.16, it seems mdate-sh was changed to compute the dates using UTC
(ChangeLog entry below, describing exactly what you saw, it seems),
with these lines:

    # Use UTC to get reproducible result.
    TZ=UTC0
    export TZ

You can get the latest mdate-sh from automake or gnulib and just put it
in place independent of any other updates.

If you already have the latest mdate-sh, then I'd appreciate seeing a
recipe to reproduce, hopefully with smaller than gdbm itself
.. --thanks, karl.


2017-09-15  Reiner Herrmann  <reiner@reiner-h.de>  (tiny change)

        mdate-sh: Ensure reproducible time output

        This change fixes automake bug#20314.
        [ https://debbugs.gnu.org/cgi/bugreport.cgi?bug=20314 ]

        'mdate-sh' pretty-prints the modification time of a file.  But it's
        output can vary depending on the timezone of the caller. Someone in
        timezone GMT-12 will get a different result (day) than someone in
        timezone GMT+12.  As this output is also used to create/update stamp
        files, which influence the further build process, the build result can
        vary.

        * lib/mdate-sh: Set 'TZ' to UTC which ensures reproducible output.
        * NEWS: Announce bug fix.