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

[Uwe Zeisberger <zeisberg@informatik.uni-freiburg.de>]

Johannes Schindelin wrote:
> 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).

> > 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?