Ethereal-dev: Re: [Ethereal-dev] What's the recommended way to use the patch tool?

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From: Ulf Lamping <ulf.lamping@xxxxxx>
Date: Tue, 31 Aug 2004 21:20:09 +0200
Guy Harris wrote:

Ulf Lamping wrote:

Given the file "new.diff" containing a unified diff, what is the right way to call the patch tool?


That depends on what the pathnames in "new.diff" look like.
There are "usually" two pathnames in the patch, what does the patch tool do, if they have different "lengths", e.g.:

diff -ur ../ethereal-0.10.6/epan/dissectors/packet-dcerpc.c ./epan/dissectors/packet-dcerpc.c --- ../ethereal-0.10.6/epan/dissectors/packet-dcerpc.c 2004-08-12 15:42:26.000000000 -0700
+++ ./epan/dissectors/packet-dcerpc.c    2004-08-19 18:48:32.000000000 -0700

Will the patch tool use the shorter path (in this case the second one)?

I think I would have to call "patch -p0 <new.diff" in the ethereal source root dir to patch my sources, am I correct here?

Is there a difference when the diff file contains one file "diff -u" or more files "diff -ur"?


There isn't a difference in the arguments to "patch".

(However, there is a difference in the number of times you have to run "patch" - and the number of times you have to save a patch file from mail - so I, at least, prefer it when people send a single patch file with patches for all the files to be changed.)

missunderstanding: I meant in both cases one diff file containing one file with diffs in one case and multiple files with diffs in the other case. From the answer you gave I would guess that there is no difference on how to call the patch tool.

At which position in the filesystem has the patch tool to be called?


If the pathnames are relative to the top-level source directory, or to a directory above that directory, you'd run it in the top-level source directory.

If they're relative to a *subdirectory* - for example, if somebody did a patch to "packet-ip.c" and ran "diff" or "svn diff" in the "epan/dissectors" directory - you'd run it in that subdirectory. (I would really prefer that people *NOT* submit patches like that - especially if they're only patching files that exist in multiple directories, such as "Makefile.am".)

Well, I think, the main reason why people do it that way is just that we don't have any good documentation how to make a "correct" diff file, but I'm currently working exactly on this :-)

I've took parts of your mail formatted it into docbook and put it into the developer's guide, I hope your fine with it (like the lot of information before, coming from you :-)))

Regards, ULFL