Hi Peff,

On Mon, 12 Nov 2012, Jeff King wrote:

> On Tue, Nov 13, 2012 at 01:16:01AM +0000, Johannes Schindelin wrote:
> > > We can do much better than O(number of commits), though, if we stop
> > > traversing down a path when its timestamp shows that it is too old to
> > > contain the commits we are searching for. The problem is that the
> > > timestamps cannot always be trusted, because they are generated on
> > > machines with wrong clocks, or by buggy software. This could be solved
> > > by calculating and caching a "generation" number, but last time it was
> > > discussed there was a lot of arguing and nothing got done.
> > 
> > Sadly, not only machines with skewed clocks, but in particular buggy
> > 3rd-party SCMs make this more than just problematic. In a git-svn clone
> > that was used as base for heavy Git development, I encountered quite a lot
> > of Jan 1, 1970 commits.
> Yeah. We tolerate a certain amount of skew (24 hours for --name-rev, and
> 5 broken commits in a row for --since). But the big ones are usually
> software bugs (the big kernel ones were from broken "guilt", I think) or
> broken imports (when I published a bunch of skew statistics last year,
> the interesting ones were all imports; I don't know if they were
> software bugs, or just garbage in, garbage out).
> > It just cannot be helped, we must distrust timestamps completely.
> Note that name-rev will produce wrong answers in the face of clock skew.
> And I think that you even wrote that code. :)

IIRC the cute code to short-circuit using the date is not from me. If it
is, I am very ashamed.

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