Merge branch 'jk/commit-dates-parsing-fix' into maint

Codepaths that parse timestamps in commit objects have been
tightened.

* jk/commit-dates-parsing-fix:
show_ident_date: fix tz range check
log: do not segfault on gmtime errors
log: handle integer overflow in timestamps
date: check date overflow against time_t
fsck: report integer overflow in author timestamps
t4212: test bogus timestamps with git-log

diff --cc cache.h
Simple merge

diff --cc date.c
Simple merge

diff --cc pretty.c
Simple merge

diff --cc t/t4212-log-corrupt.sh
Simple merge