Re: [PATCH] builtin-apply: check for empty files when detecting creation patch

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: May 13, 2008, 22:24 UTC
Message-ID: <alpine.LFD.1.10.0805131514300.3019@woody.linux-foundation.org>
In-Reply-To: <7vprrpswof.fsf@gitster.siamese.dyndns.org>

On Tue, 13 May 2008, Junio C Hamano wrote:

> 
> So I think it is reasonable to use non-/dev/null-ness of first as a cue
> that it is not a creation patch.

I disagree.

The fact is, /dev/null means that for patches generated by GNU diff, but a lot of other systems you'll find that it means no such thing.

Look at CVS-generated patches, or SVN for that matter. The diffs look like this:

	Index: file
	===================================================================
	--- file (revision 0)
	+++ file (working copy)
	@@ -0,0 +1 @@
	+test

and there is no /dev/null there.

The thing is, git-apply is careful, and it's very much careful with respect to *knowing* that there are lots of different versions of "diff" floating around, and lots of different SCM systems that generate odd diff headers. We should absolutely NOT start expecting that diffs are only generated with GNU diff.

So non-/dev/null'ness means absolutely nothing. It means "don't know", and we should leave is_new and is_delete as -1.

		Linus