On Tue, 11 Dec 2007, Linus Torvalds wrote:
quoted text
> 
> We do that. The expense for git is that we don't do the revisions as a 
> single file at all. We'll look through each commit, check whether the 
> "gcc" directory changed, if it did, we'll go into it, and check whether 
> the "ChangeLog" file changed - and if it did, we'll actually diff it 
> against the previous version.

And, btw: the diff is totally different from the xdelta we have, so even 
if we have an already prepared nice xdelta between the two versions, we'll 
end up re-generating the files in full, and then do a diff on the end 
result.

Of course, part of that is that git logically *never* works with deltas, 
except in the actual code-paths that generate objects (or generate packs, 
of course). So even if we had used a delta algorithm that would be 
amenable to be turned into a diff directly, it would have been a layering 
violation to actually do that.

Other systems can sometimes just re-use their deltas to generate the 
diffs and/or blame information. I dunno whether SVN does that. CVS does, 
afaik.

			Linus
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