Re: "git-diff-tree -R A B == git-diff-tree B A"?

From: Linus Torvalds <torvalds@osdl.org>
Date: May 20, 2005, 15:53 UTC
Message-ID: <Pine.LNX.4.58.0505200844090.2206@ppc970.osdl.org>
In-Reply-To: <7vzmupud54.fsf@assigned-by-dhcp.cox.net>

On Fri, 20 May 2005, Junio C Hamano wrote:

>
> Keep git-diff-tree output sorted in cache order on dir/file swap.

No, this is wrong.

Or rather, it is incomplete - it gets only a small subset of the interesting cases right.

You need to really teach diff-tree about directory sorting, because it is more complicated than you think.

The sorting does _not_ just affect files/directories with the same names. It affects files and directories that have the same _beginning_.

The only correct way to do name sorting is the one that fsck does in "verify_order()". To realize why, you need to realize that "A" (the directory) sorts _after_ a filename "A file", because '/' sorts after ' '.

In contrast, "A" (the directory) sorts _before_ "ABBA" (the band), because '/' sorts before 'B'.

-- 
Side note:

Btw, right now I depend on "memcmp()" doing comparisons as "unsigned
char", which is supposed to be true, but I don't know whether it's 
entirely portable. So it might be that I should implement my own 
"namecmp()" entirely from scratch.

Does anybody know if some broken system does "memcmp" ordering on signed 
chars?

		Linus