Re: [Monotone-devel] another newbie question - nonlinear ordering

[eli . carter]

On Wed, 2005-04-20 at 14:49 -0500, K. Richard Pixley wrote:
> Start with an empty file, f0.  Apply some initial content, delta1.
> 
> f0 + delta1 = f1
> 
> It occurs to me that if I now apply a change, delta2, to this file,  
> (tree, subtree, repository, whatever):
> 
> f1 + delta2 = f2
> 
> And then I back out that change by applying the inverse delta2,
> delta2',  
> then:
> 
> f2 + delta2' = f3 = f1.
> 
> Since the hash for f3 and f1 will be identical, we can no longer
> talk  
> meaningfully about a linear sequence of revisions.  That is, revision
> id  
> = SHA1(f3) = SHA1(f1) no longer has a single ancestor nor is there  
> necessarily even a deterministic path from f3 back to the empty
> file.   
> f3 and f1 are different not in content, but only in ancestry.
> 
> Is this history really lost in monotone?  Or how is this handled?

The file for f3 may be identical to f1, but the parent will not be, and
that is part of the input to the hash.  Thereby preventing cycles from
occuring.

HTH,

Eli
-- 
-------------------. "If it ain't broke now,
Eli Carter          \                   it will be soon." -- crypto-gram
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