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