If an ident line has a ridiculous date value like (2^64)+1,
we currently just pass ULONG_MAX along to the date code,
which can produce nonsensical dates.
On systems with a signed long time_t (e.g., 64-bit glibc
systems), this actually doesn't end up too bad. The
ULONG_MAX is converted to -1, we apply the timezone field to
that, and the result ends up somewhere between Dec 31, 1969
and Jan 1, 1970.
However, there is still a few good reasons to detect the
overflow explicitly:
1. On systems where "unsigned long" is smaller than
time_t, we get a nonsensical date in the future.
2. Even where it would produce "Dec 31, 1969", it's easier
to recognize "midnight Jan 1" as a consistent sentinel
value for "we could not parse this".
3. Values which do not overflow strtoul but do overflow a
signed time_t produce nonsensical values in the past.
For example, on a 64-bit system with a signed long
time_t, a timestamp of
18446744073000000000 produces a
date in 1947.
We also recognize overflow in the timezone field, which
could produce nonsensical results. In this case we show the
parsed date, but in UTC.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>