Merge branch 'hm/config-parse-expiry-date'

"git config --expiry-date gc.reflogexpire" can read "2.weeks" from
the configuration and report it as a timestamp, just like "--int"
would read "1k" and report 1024, to help consumption by scripts.

* hm/config-parse-expiry-date:
  config: add --expiry-date

diff --cc config.c
Simple merge

diff --cc config.h
Simple merge