bug#32931: time-stamp-format: offer numeric time zones too

[Robert Pluim]

>>>>> On Wed, 06 Nov 2019 08:48:46 -0800, Stephen Gildea 
>>>>> <stepheng+emacs@gildea.com> said:

    Stephen> Version: 27.1
    Stephen> commit: 9ce67baa9a3733ae93885b6242130497b13c8703
    Stephen> time-stamp: implement numeric time zone conversion

    Stephen> * time-stamp.el: Implement %:z as expanding to the numeric time 
zone
    Stephen> offset, to address the feature request of bug#32931.  Do not 
document it
    Stephen> yet, to discourage compatibility problems in mixed Emacs 26 and 
Emacs 27
    Stephen> environments.  Documentation will be added in a subsequent release 
at
    Stephen> least two years later.  (We cannot yet use %z for numeric time zone
    Stephen> because in Emacs 26 it was documented to do something else.)

    Stephen> * time-stamp-tests.el (time-stamp-test-format-time-zone): expand 
this
    Stephen> test and break it into two tests, 
time-stamp-test-format-time-zone-name
    Stephen> and time-stamp-test-format-time-zone-offset.

If youʼre going to be making changes without documenting them, the
least you can do is follow the commit format conventions.

I donʼt see any reason for not documenting this, you can make it clear
that people mixing emacs 26 and 27 need to be careful.

Robert