Date: Sun, 08 Oct 2000 20:59:18 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
Sender: halo1 AT zahav DOT net DOT il
To: rich AT phekda DOT freeserve DOT co DOT uk
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In-reply-to: <39E0B5A5.B1C9E9FE@phekda.freeserve.co.uk> (message from Richard
	Dawe on Sun, 08 Oct 2000 18:57:57 +0100)
Subject: Re: Bizarre patch behaviour
References: <39E06A7C DOT 9BD27470 AT phekda DOT freeserve DOT co DOT uk> <3028-Sun08Oct2000173759+0300-eliz AT is DOT elta DOT co DOT il> <39E0B5A5 DOT B1C9E9FE AT phekda DOT freeserve DOT co DOT uk>
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> Date: Sun, 08 Oct 2000 18:57:57 +0100
> From: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
> 
> Eli Zaretskii wrote:
> > Take a look at the section named "NOTES FOR PATCH SENDERS" in the
> > Patch man page.  You have violated one of the rules it sets: not to
> > produce diffs where the OLD and the NEW files have different number of
> > slashes.  This is especially important if the patch is supposed to be
> > applied with the -pN switch, as you did.
> 
> Oops, you are quite right. The info docs don't seem to mention this, as
> far as I can tell.

The Info docs are terribly outdated, as far as Patch is concerned
(they are accurate about Diff and friends, though); I think there's a
note somewhere in the Patch distro about this.  You should use the
Patch man page instead.

> I wonder if this should be added to:
> 
>     info diffutils 'Making Patches'
> 
> just to clarify for ignorant people like me. ;)

Sure.  Feel free to suggest this to Paul Eggert, the maintainer of
Diffutils and Patch (although I imagine that he knows).

> > Because Patch uses some complicated guesswork to find out which file
> > to apply the patch to (it's not easy, contrary to how it sounds), and
> > that guesswork sometimes breaks.
> 
> Oh, OK, I thought it only used the first filename and ignored the second.

It can't, in general.  If it did, the following wouldn't DTRT:

	  diff -c foo.c~ foo.c > foo.dif
	  patch -p0 < foo.dif

This example is very frequently seen, and the second file name is the
one you want Patch to pick up in such cases.