Merge branch 'rs/strbuf-addftime-zZ'

As there is no portable way to pass timezone information to
strftime, some output format from "git log" and friends are
impossible to produce.  Teach our own strbuf_addftime to replace %z
and %Z with caller-supplied values to help working around this.

* rs/strbuf-addftime-zZ:
  date: use localtime() for "-local" time formats
  t0006: check --date=format zone offsets
  strbuf: let strbuf_addftime handle %z and %Z itself

diff --cc Documentation/rev-list-options.txt
Simple merge

diff --cc date.c
index 63fa99685e288bd79c75fd6af983f8b628a08fed,5580c40ac094211cb3d378b5b523a63308de0a2d..1fd6d663758de5a4b9d7f395b16716864317ed84
--- 1/date.c
--- 2/date.c
+++ b/date.c
@@@ -70,6 -60,12 +70,12 @@@ static struct tm *time_to_tm(timestamp_
        return gmtime(&t);
  }
  
 -static struct tm *time_to_tm_local(unsigned long time)
++static struct tm *time_to_tm_local(timestamp_t time)
+ {
+       time_t t = time;
+       return localtime(&t);
+ }
+ 
  /*
   * What value of "tz" was in effect back then at "time" in the
   * local timezone?

diff --cc t/t0006-date.sh
index 42d4ea61ef531d8c495c5c2216d434982f1c6182,8e219b7c51fead82d81c049f8d1948016dc823e1..7ac9466d5055e02179467fa9e41004bbc89df6dc
--- 1/t/t0006-date.sh
--- 2/t/t0006-date.sh
+++ b/t/t0006-date.sh
@@@ -51,10 -53,20 +53,20 @@@ check_show iso-local "$TIME" '2016-06-1
  check_show raw-local "$TIME" '1466000000 +0000'
  check_show unix-local "$TIME" '1466000000'
  
+ check_show 'format:%z' "$TIME" '+0200'
+ check_show 'format-local:%z' "$TIME" '+0000'
+ check_show 'format:%Z' "$TIME" ''
+ check_show 'format-local:%Z' "$TIME" 'UTC'
+ check_show 'format:%%z' "$TIME" '%z'
+ check_show 'format-local:%%z' "$TIME" '%z'
+ 
+ check_show 'format:%Y-%m-%d %H:%M:%S' "$TIME" '2016-06-15 16:13:20'
+ check_show 'format-local:%Y-%m-%d %H:%M:%S' "$TIME" '2016-06-15 09:13:20' '' EST5
+ 
  # arbitrary time absurdly far in the future
  FUTURE="5758122296 -0400"
 -check_show iso       "$FUTURE" "2152-06-19 18:24:56 -0400" LONG_IS_64BIT
 -check_show iso-local "$FUTURE" "2152-06-19 22:24:56 +0000" LONG_IS_64BIT
 +check_show iso       "$FUTURE" "2152-06-19 18:24:56 -0400" TIME_IS_64BIT,TIME_T_IS_64BIT
 +check_show iso-local "$FUTURE" "2152-06-19 22:24:56 +0000" TIME_IS_64BIT,TIME_T_IS_64BIT
  
  check_parse() {
        echo "$1 -> $2" >expect