[RFC]New style of revision id [Was Re: VCS comparison table]

[Aaron Bentley]

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Martin Pool wrote:
> On Tue, 2006-10-24 at 00:17 +0200, Goffredo Baroncelli wrote:
> 
>>But I agree with Linus that the testament ( the bzr checksum ) isn't very 
>>integrated with the usual bazaar workflow as the git "revision-ID".
>>
>>From a bazaar developer point of view I think if it is possible to switch from 
>>a pseudo-random revidion id, to a checksum basis revision id: the checksum 
>>can be computed on the basis of the sha1 of the files, and 
>>timestamp/commiter/parent-revision(s)/properties.
>>
>>This new style of revid can be in the form
>><user>@<host>-<date>-<cksum>
>>
>>Yes, the first three field are redundant: but so the change isn't too 
>>dramatic ! :-)
> 
> 
> I think storing or naming those objects by their hash is a pretty
> interesting idea, and I've warmed to it after this discussion.  As you
> say it should pretty much drop in to the existing framework.

I'm a bit more suspicious.  So far, we've had 3 major testament formats.
 The most recent one is very new, and there's only a strict form-- i.e.
the last-modified info is part of this testament.  I'm not sure whether
we've finally stabilized, and I'm not sure whether the "3 strict" format
is suitable for this.

Also, I'm not sure whether we can correctly calculate a testament before
we know the revision-id.

I guess there's some advantage of having a checksum in the revision-id.
 I'm not against it per se, just cautious.

Aaron
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