Merge branch 'jc/parse-date-raw' into maint

* jc/parse-date-raw:
parse_date(): '@' prefix forces git-timestamp
parse_date(): allow ancient git-timestamp

diff --cc builtin/commit.c
Simple merge

diff --cc date.c
Simple merge

diff --cc git-sh-setup.sh
Simple merge

diff --cc t/t3400-rebase.sh
Simple merge