Re: [PATCH] Fix -B "very-different" logic.

From: Linus Torvalds <torvalds@osdl.org>
Date: Jun 3, 2005, 00:21 UTC
Message-ID: <Pine.LNX.4.58.0506021716140.1876@ppc970.osdl.org>
In-Reply-To: <7vll5sz54z.fsf_-_@assigned-by-dhcp.cox.net>

On Thu, 2 Jun 2005, Junio C Hamano wrote:

Show 6 quoted lines

> 
> However I think the diffcore-break algorithm itself was basing
> its "very_different" computation on numbers somewhat bogus.  It
> was counting newly inserted bytes into account, but amount of
> those bytes should not make any difference when determining if
> the change is a complete rewrite.

Careful.

I think the amount of new code _should_ matter. Otherwise, an old empty file would always be considered the source of a new file, since the diff doesn't remove anything. Similarly, just because we have a boilerplate file shouldn't make that always be considered a "wonderful source", when people add the real meat to it.

So I think you're on the right track, but I don't think you should entirely dismiss "lots of stuff added" as a reason for a "break". I think that if the new stuff is _much_ larger than the old stuff, it might as well be considered a rewrite.

In particular, let's say that I used to have two files:

	a.c - small helper functions
	b.c - the "meat" of the thing

and I end up deciding that I might as well collapse it all into one file, a.c. What happens? There's almost no deletes from a.c, but there's a lot of new code in it.

Wouldn't it be _better_ if you considered the new "a.c" a new file, so that you might notice that it's actually _closer_ to the old removed "b.c" than the old "a.c"?

See what I'm saying?

		Linus