Re: git and time

From: Junio C Hamano <junkio@cox.net>
Date: Sep 28, 2006, 17:28 UTC
Message-ID: <7vodszuche.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.64.0609281003070.3952@g5.osdl.org>

Linus Torvalds <torvalds@osdl.org> writes:

Show 18 quoted lines

> On Thu, 28 Sep 2006, Matthew L Foster wrote:
>> 
>> I am not saying git should "police any one else's clocks", I am saying git should be designed or
>> configured in such a way, using local time, that it obviates the current reliance on everyone
>> else's clock being set correctly. 
>
> Matt!
>
> THERE IS NO SUCH RELIANCE! NONE.
>
> Trust me. When we say that git ignores time, WE MEAN IT. Git does not rely 
> on time, git does not use time, git does not CARE!
>
> Please stop looking at gitweb _immediately_. If you think time has some 
> meaning for git, stop. It doesn't. We've told you over and over and over 
> again that there is absolutely _zero_ reliance on everybody else's clock 
> being set correctly. The damn clock could go _backwards_, or make huge 
> jumping purple leaps of imagination, and git wouldn't care.

I think Matthew means (by "relying") that everybody's clock must be set correctly in order for us to show the commits in gitweb or rev-list output so that their timestamps are monotonically decreasing (because we list things from newer to older). I sympathise.

We order things by causality (i.e. ancestry order), but that unfortunately (!!) happens to match timestamp order for simple history made on a single machine. This can easily lead to such a misunderstanding that we are somehow trying to show things in linear time order, hence we subscribe to the notion of global, uniform and monotonic time.

Of course, we don't.