New zic -b option to shrink data and test y2038

* Makefile (ZFLAGS): Mention -b in comment.
* NEWS: Mention this.
* zic.c (usage): Mention -b.
(bloat): New static var.
(want_bloat): New static function.
(main): Parse new -b option.
(writezone): In slim output, suppress QTBUG-53071 workaround,
pre-2011 bug workaround, all-zero isstdcnt and isutcnt indicators,
and 32-bit data (except for header and the single type that RFC
8536 requires).
(outzone): In slim output, suppress redundant transitions back to
1900 or forward through 2038, and suppress redundant transitions
just before the TZ string takes over.
* zic.8: Document -b.  Sort options alphabetically.

1 files changed, 38 insertions, 9 deletions

diff --git a/zic.8 b/zic.8
index 89ea2d9..d02994f 100644
--- a/zic.8
+++ b/zic.8
@@ -45,6 +45,32 @@ Output version information and exit.
 .B \*-\*-help
 Output short usage message and exit.
 .TP
+.BI "\*-b " bloat
+Output backward-compatibility data as specified by
+.IR bloat .
+If
+.I bloat
+is
+.BR fat ,
+generate additional data entries that work around potential bugs or
+incompatibilities in older software, such as software that mishandles
+the 64-bit generated data.
+If
+.I bloat
+is
+.BR slim ,
+keep the output files small; this can help check for the bugs
+and incompatibilities.
+Although the default is currently
+.BR fat ,
+this is intended to change in future
+.B zic
+versions, as software that mishandles the 64-bit data typically
+mishandles timestamps after the year 2038 anyway.
+Also see the
+.B \*-r
+option for another way to shrink output size.
+.TP
 .BI "\*-d " directory
 Create time conversion information files in the named directory rather than
 in the standard directory named below.
@@ -59,6 +85,11 @@ will act as if the input contained a link line of the form
 .ti +.5i
 Link	\fItimezone\fP		localtime
 .TP
+.BI "\*-L " leapsecondfilename
+Read leap second information from the file with the given name.
+If this option is not used,
+no leap second information appears in output files.
+.TP
 .BI "\*-p " timezone
 Use
 .IR timezone 's
@@ -70,15 +101,6 @@ will act as if the input contained a link line of the form
 .ti +.5i
 Link	\fItimezone\fP		posixrules
 .TP
-.BI "\*-t " file
-When creating local time information, put the configuration link in
-the named file rather than in the standard location.
-.TP
-.BI "\*-L " leapsecondfilename
-Read leap second information from the file with the given name.
-If this option is not used,
-no leap second information appears in output files.
-.TP
 .BR "\*-r " "[\fB@\fP\fIlo\fP][\fB/@\fP\fIhi\fP]"
 Reduce the size of output files by limiting their applicability
 to timestamps in the range from
@@ -102,6 +124,13 @@ On platforms with GNU
 .BR date ,
 .q "zic \-r @$(date +%s)"
 omits data intended for past timestamps.
+Also see the
+.B "\*-b slim"
+option for another way to shrink output size.
+.TP
+.BI "\*-t " file
+When creating local time information, put the configuration link in
+the named file rather than in the standard location.
 .TP
 .B \*-v
 Be more verbose, and complain about the following situations: