Date: Sun, 08 Oct 2000 17:37:59 +0200
From: "Eli Zaretskii" <eliz AT is DOT elta DOT co DOT il>
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To: rich AT phekda DOT freeserve DOT co DOT uk
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In-reply-to: <39E06A7C.9BD27470@phekda.freeserve.co.uk> (message from Richard
	Dawe on Sun, 08 Oct 2000 13:37:16 +0100)
Subject: Re: Bizarre patch behaviour
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> Date: Sun, 08 Oct 2000 13:37:16 +0100
> From: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
> 
>     diff -pPrC3 . /develop/ports/gnu.dev/filutil4.0 > [some-dir]/diffs
>
> and then try to apply the patch another fresh copy of the Fileutils
> sources:
> 
>     patch -p0 -i [some-dir]/diffs
> 
> then patch tries to patch the files in /develop/ports/gnu.dev/filutil4.0!

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.

It is usually best to have the old and the new files either in the
same directory (and then obviously under different names/extensions,
like *.c and *.bak), or in sibling directories that both have the same
depth relative to some common parent.  In the second case, run Diff
from that common parent, to yield the same number of slashes in both
OLD and NEW files.

> Why does it apply
> all differences to files present in the original distribution OK and then
> change direction for the new files?

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.