On Monday 2006 November 20 10:48, Junio C Hamano wrote:
> I wrote the code and you contradict me ;-)?
Sorry; I wasn't so much contradicting that the filtering works exactly as you
say (of course it must - I don't know anywhere near enough to make that sort
of assertion).
However, I do think that the problem is not one of filtering. I was saying
that "-C" has no practical use.
> in your example, it would give you the creation of fileB, not
> copy.
I'm sure it would - but you had to use --find-copies-harder; -C would not find
it as a copy.
> - Renames are only picked up from files that were lost in the
> same change (i.e. "mv fileA fileB" creates fileB and loses
> fileA; fileB is checked if it is similar to fileA in the
> original).
I've found rename detection to be flawless in all my uses.
> - Copies are only picked up from files that were changed in the
> same change (i.e. splitting major part of original file and
> moving it to somewhere else, while leaving a skelton in the
> original file). "harder" is needed if the copy original was
> untouched, as you found out.
Yep; I understand that. I also understand that it is done for performance
reasons. However, since the typical copy will be one where the source
doesn't change at the same time, I am arguing that the non-hard copy
detection isn't much use.
> The last one is a compromise between performance and thoroughness,
> and the "harder" is one knob to tweak its behaviour.
I've been poking in tree-diff.c to see if I can understand why it it such a
performance hog. I still haven't. Each file is stored under its hash right?
So for copy detection why can't you just search for other files with the same
hash, which I presume is very fast (as it is the basis of what makes git so
fast)?
I am probably misunderstanding git, but I guess that a copy isn't even needed
in the database because two files with the same hash in the working copy only
need storing once and then referencing twice. So for a copy (again, with my
simple understanding of git) we'd have:
commit1 -> tree1 -> fileA = fileA_hash
^
|
commit2 -> tree2 -> fileA = fileA_hash
fileB = fileB_hash
Doesn't that mean that copy detection is just a matter of searching the parent
commit trees for references to the same hash?
Andy
--
Dr Andy Parkins, M Eng (hons), MIEE
andyparkins@xxxxxxxxx
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