Re: Fix up diffcore-rename scoring

From: Junio C Hamano <junkio@cox.net>
Date: Mar 13, 2006, 06:46 UTC
Message-ID: <7vmzfusuyq.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.64.0603122223160.3618@g5.osdl.org>

Linus Torvalds <torvalds@osdl.org> writes:

Show 10 quoted lines

> The "score" calculation for diffcore-rename was totally broken.
>
> It scaled "score" as
>
> 	score = src_copied * MAX_SCORE / dst->size;
>
> which means that you got a 100% similarity score even if src and dest were 
> different, if just every byte of dst was copied from src, even if source 
> was much larger than dst (eg we had copied 85% of the bytes, but _deleted_ 
> the remaining 15%).

Your reading of the code is correct, but that is deliberate.

>  	/* How similar are they?
>  	 * what percentage of material in dst are from source?
>  	 */

I wanted to say in such a case that dst was _really_ derived from the source. I think using max may make more sense, but I need to convince myself by looking at filepairs that this change stops detecting as renames, and this change starts detecting as renames.