[tz] Regarding timezone upgrade from 2017c to 2018c

[Paul Eggert]

On 03/02/2018 05:16 AM, Debananda Pal wrote:
> While upgrading to 2018c timezone, I found below changes :
>
> ./etc/localtime  ./etc/localtime    ==> Newly added
> ./etc/zoneinfo/localtime -> GMT ==> This entry is removed
>
> ./etc/zoneinfo/GMT  ./etc/zoneinfo/GMT  ==> Changed to ==> 
> ./etc/zoneinfo/GMT link ./etc/localtime

Most likely you're observing effects of the change that was proposed here:

https://mm.icann.org/pipermail/tz/2017-December/025783.html

If by "." you mean the root of the destination directory, then yes, the 
link that used to be in ./etc/zoneinfo/localtime is now in 
./etc/localtime by default. This is a link to the GMT file (a file that 
used to be in ./etc/zoneinfo/GMT and is now in 
./usr/share/zoneinfo/GMT). You can restore the old behavior by setting 
the appropriate Makefile macro.

> ./etc/zoneinfo/US/Pacific-New -> ../America/Los_Angeles ==>  This 
> entry is removed

Yes, that's a consequence of the change proposed here:

https://mm.icann.org/pipermail/tz/2017-November/025476.html


> ./etc/zoneinfo/Africa/Sao_Tome -> ../Atlantic/St_Helena  ==> Changed to
>   ==>  ./etc/zoneinfo/Africa/Sao_Tome ./etc/zoneinfo/Africa/Sao_Tome

Yes, São Tomé and Príncipe got its own Zone, due to the change proposed 
here:

https://mm.icann.org/pipermail/tz/2018-January/025802.html

In general, if you are curious about changes like this, it's a good idea 
to clone the git repository here:

https://github.com/eggert/tz

You can then use commands like "git blame" to find out when things 
changed and why. For example, if you're curious about Africa/Sao_Tome, 
the command "git blame africa" outputs the the following lines, which 
identify the IDs and dates of the most-recent revisions affecting lines 
in Africa/Sao_Tome (there have been three so far this year, as it happens):

2951fa3b (Paul Eggert        2018-01-08 09:03:13 -0800 1068) Zone 
Africa/Sao_Tome     0:26:56 -    LMT    1884
fff7816c (Paul Eggert        2018-02-16 16:11:42 -0800 1069)     
-0:36:45 -    LMT    1912 Jan  1 00:00u # Lisbon MT
a4272fbf (Paul Eggert        2018-01-08 16:12:21 -0800 1070)     
  0:00    -    GMT    2018 Jan  1 01:00
2951fa3b (Paul Eggert        2018-01-08 09:03:13 -0800 1071)     
  1:00    -    WAT

You can then issue commands like "git log 2951fa3b^!" and "git log 
2951fa3b^!" to find more details about each of the three changes.

Come to think of it, something like the above should be in the file 
CONTRIBUTING. Proposed patch attached.

-------------- next part --------------
From 1ff6e2449ad9593de45cc452f263f8be18a92c3d Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert at cs.ucla.edu>
Date: Fri, 2 Mar 2018 09:38:18 -0800
Subject: [PATCH] =?UTF-8?q?*=20CONTRIBUTING:=20Mention=20=E2=80=98git=20bl?=
 =?UTF-8?q?ame=E2=80=99.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 CONTRIBUTING | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/CONTRIBUTING b/CONTRIBUTING
index 716f32b..0cfc77f 100644
--- a/CONTRIBUTING
+++ b/CONTRIBUTING
@@ -25,7 +25,8 @@ justification.  Citations should use https: URLs if available.
 
 Please submit changes against either the latest release in
 <https://www.iana.org/time-zones> or the master branch of the development
-repository.  If you use Git the following workflow may be helpful:
+repository.  The latter is preferred.  If you use Git the following
+workflow may be helpful:
 
   * Copy the development repository.
 
@@ -42,6 +43,12 @@ repository.  If you use Git the following workflow may be helpful:
 
       git checkout -b mybranch
 
+  * Sleuth by using 'git blame'.  For example, when fixing data for
+    Africa/Sao_Tome, if the command 'git blame africa' outputs a line
+    '2951fa3b (Paul Eggert 2018-01-08 09:03:13 -0800 1068) Zone
+    Africa/Sao_Tome 0:26:56 - LMT 1884', commit 2951fa3b should
+    provide some justification for the 'Zone Africa/Sao_Tome' line.
+
   * Edit source files.  Include commentary that justifies the
     changes by citing reliable sources.
 
@@ -67,6 +74,9 @@ repository.  If you use Git the following workflow may be helpful:
 
       git send-email master
 
+    For an archived example of such an email, see
+    <https://mm.icann.org/pipermail/tz/2018-February/026122.html>.
+
   * Start anew by getting current with the master branch again
     (the second step above).
 
-- 
2.14.3