Re: [PATCH] Additional merge-base tests

From: A Large Angry SCM <gitzilla@gmail.com>
Date: Jul 4, 2006, 23:07 UTC
Message-ID: <44AAF49F.6090008@gmail.com>
In-Reply-To: <Pine.LNX.4.63.0607050021330.29667@wbgn013.biozentrum.uni-wuerzburg.de>

Johannes Schindelin wrote:

Show 19 quoted lines

> Hi,
> 
> On Tue, 4 Jul 2006, Junio C Hamano wrote:
> 
>> Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
>>
>>> We could introduce a time.maximumSkew variable, and just walk only 
>>> that much further when traversing the commits.
>> We could have had "commit generation number" in the commit
>> object header, and use that instead of commit timestamps for
>> these traversal purposes.  The generation number for a commit is
>> defined to be max(generation number of its parents)+1 and we
>> prime the recursive this definition by defining the generation
>> number for the root commit to be one.
> 
> Are you really, really sure this is a remedy? I, for one, am quite sure of 
> the opposite. What you propose is just another time scale, only this time, 
> it is not universally true (not even minus local incompetence to keep the 
> clock accurate).

It works[*] and it does what using the timestamp was trying to do. Namely, work from "more recent" (or "closer") commits toward "older" (or "farther") commits until you've gone past the point you care about.

It's a little late to be changing the structure of a commit and you'd have to deal with some size/scale issues, but it's do-able. A better idea may be to generate and keep the generation number on a per repository basis, and you'd be able to work around changing grafts.

[*] Grafts do _really_ nasty things to this. Just like clock skew does now.