Re: [PATCH] Use diff3 instead of merge in merge-recursive.

From: Uwe Zeisberger <zeisberg@informatik.uni-freiburg.de>
Date: Oct 20, 2006, 21:11 UTC
Message-ID: <20061020211121.GB3024@cepheus.pub>
In-Reply-To: <Pine.LNX.4.63.0610181135120.14200@wbgn013.biozentrum.uni-wuerzburg.de>

Johannes Schindelin wrote:

Show 10 quoted lines

> Hi Uwe,
> 
> On Wed, 18 Oct 2006, Uwe Zeisberger wrote:
> 
> > If no error occurs, merge (from rcs 5.7) is nothing but:
> > 
> > 	diff3 -E -am -L label1 -L label2 -L label3 file1 file2 file3 > tmpfile
> > 	cat tmpfile > file1
> 
> Interesting.

> I wonder if we could streamline the code such that index_fd 
> is called directly on the output of diff3? Of course, the result has to be 
> removed when the call to diff3 fails.

I thought about that, too. But my primary intention was to get rid of 'merge', because the Solaris boxes I use from time to time lack merge, but have (GNU) diff3[1]. I already had a mental note to look into that.

If Linus is right that there are systems that have merge but lack diff3, then a combined approach is maybe the best? That is, try diff3 and if that is missing, try merge. (Or the other way round if you prefer.)

OK, I looked a bit deeper into rcs, and it seems to handle the BSD diff3 case. So Linus might be right.

BTW, merge -p sends the merged result to stdout instead of overwriting the first file given. That is

	merge -p -L label1 -L label2 -L label3 file1 file2 file3

and (GNU)

	diff3 -E -am -L label1 -L label2 -L label3 file1 file2 file3

are exactly equivalent. So if that option of merge is old enough, these are the candidates for the "combined approach" (see above).

Show 8 quoted lines

> > I didn't made any timing tests or further tests for correctness, but I
> > hope Johannes still has the framework from the time when he converted
> > the Python script to C?  
> > 
> > @Johannes: If so, could you test this patch?
> 
> I have to dig a little where I have it, but I think I can give it a try in 
> a few hours (imagine this lyrics to the melody of the day job blues).

Seems to be a long blues because you didn't sent any results. :-(

Best regards Uwe

[1] They also have a version of diff3 (I guess from BSD) that is not suited to be used for merging, at least rcs' merge cannot use it.

-- 
Uwe Zeisberger

If a lawyer and an IRS agent were both drowning, and you could only save
one of them, would you go to lunch or read the paper?