lib/time: add README, update.bash script
R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5674104
diff --git a/lib/time/update.bash b/lib/time/update.bash
new file mode 100755
index 0000000..30ca2c7
--- /dev/null
+++ b/lib/time/update.bash
@@ -0,0 +1,45 @@
+#!/bin/sh
+# Copyright 2012 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+# This script rebuilds the time zone files using files
+# downloaded from the ICANN/IANA distribution.
+
+# Versions to use.
+CODE=2011i
+DATA=2011n
+
+set -e
+rm -rf zoneinfo work
+mkdir zoneinfo work
+cd work
+curl -O http://www.iana.org/time-zones/repository/releases/tzcode$CODE.tar.gz
+curl -O http://www.iana.org/time-zones/repository/releases/tzdata$DATA.tar.gz
+tar xzf tzcode$CODE.tar.gz
+tar xzf tzdata$DATA.tar.gz
+
+# Turn off 64-bit output in time zone files.
+# We don't need those until 2037.
+perl -p -i -e 's/pass <= 2/pass <= 1/' zic.c
+
+make CFLAGS=-DSTD_INSPIRED AWK=awk TZDIR=../zoneinfo posix_only
+
+# America/Los_Angeles should not be bigger than 1100 bytes.
+# If it is, we probably failed to disable the 64-bit output, which
+# triples the size of the files.
+size=$(ls -l ../zoneinfo/America/Los_Angeles | awk '{print $5}')
+if [ $size -gt 1200 ]; then
+ echo 'zone file too large; 64-bit edit failed?' >&2
+ exit 2
+fi
+
+cd ..
+hg addremove zoneinfo
+echo
+if [ "$1" == "-work" ]; then
+ echo Left workspace behind in work/.
+else
+ rm -rf work
+fi
+echo New time zone files in zoneinfo/.
