Re: [PATCH v4] gc: call "prune --expire 2.weeks.ago" by default

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Wed, 12 Mar 2008, Junio C Hamano wrote:

> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> 
> >> Yuck; approxidate() returns ulong.  Can subtracting a ulong from 
> >> another ever go negative?
> >> 
> >> Besides, because there is no guarantee of the order of evaluation 
> >> between these two approxidate() calls, you may get +1 or -1 on the 
> >> second boundary.
> >> 
> >> I think the reason why you did not catch it in your test is because 
> >> your tests are half complete; they test only what you wanted to catch 
> >> (misconfigured case) and do not test the other half (properly working 
> >> case).
> >
> > Yes, probably.  Of course, comparing a difference to 0 is absolutely 
> > moronic.
> >
> > I should have written
> >
> > 				approxidate(value) >= approxidate("now"))
> >
> > in the first place.
> 
> Eh, sorry, but why?

The thing is: I want to prevent invalid dates in gc.pruneExpire from going 
unnoticed, _especially_ since they would default to "now".  IOW if you 
said something like "one.weak.ago", it would actually have the same effect 
as "now" and offer _no_ grace period.

But like you said, comparing the difference of two unsigned longs to >= 0 
might be quite stupid.  Instead, I compare them _directly_.

Since I compare the value to "now" first, and only if it is not, compare 
the approxidate() of the value to the current time stamp, I can verify 
that no invalid date was specified.

Unfortunately, this check includes future dates.  Fortunately, they do not 
make sense at all.

To make my reasoning clear, how about this comment above that if() clause?

		/*
		 * In case of an invalid date, approxidate() returns the
		 * same as approxidate("now").  Since the millisecond
		 * boundary could have been crossed between the two calls
		 * to approxidate(), we compare not only for equality,
		 * but also if the former is greater than the latter.
		 *
		 * Note: this assumes that future dates are invalid, which
		 * makes sense, really.
		 */

Hmm?

Ciao,
Dscho