[plug] Merging 2 files, CVS-style

[Peter Wright]

On Thu, Apr 13, 2000 at 12:37:28PM +0800, Nick Bannon offered the
following solution:
> On Thu, Apr 13, 2000 at 11:04:36AM +0800, Peter Wright wrote:
> [...]
> > I'm working on a software project using CVS for version control, which
> > I'm guessing at least a few of you should be familiar with. Now CVS
> > has a very nice conflict-resolution merging facility - when you've
> > changed an old revision of a file and then try to update it, it marks
> [...]
> 
> I think your problem is tricky - the way CVS works is that it has
> _three_ files to compare - two plus a common ancestor. If the
> ancestor and version 1 differ, it'll merge it in. If the ancestor
> and version 2 differ, it'll merge it in. If all three differ, it's a
> conflict.
> 
> Using RCS (which CVS is built on), the following seems to work.
[ snip suggested solution, which does indeed work ]

Thanks very much for that Nick... but....

> Nick.

On Thu, Apr 13, 2000 at 01:43:31PM +0800, Mike Holland explained why
we're going to kick ourselves: 
> On Thu, 13 Apr 2000, Nick Bannon wrote:
> > I think your problem is tricky - the way CVS works is that it has
> > _three_ files to compare - two plus a common ancestor. If the
> > ancestor and
> 
> Quite right, but gee guys ... you'll kick yourselves.
> 
> % man -k merge
> merge (1)            - three-way file merge
[ snip ]
> Does this work? Hope that helps.

*kicks self*

<cartman>Gahddammittt!!!!</cartman>

I'd _just_ finished writing a script implementing Nick's solution above
using the RCS utilities ci, co, rcsmerge. Sigh. :)

Oh well, at least some of it can be salvaged, as the "original" file
still needs to be generated. For those who might be interested, I've
attached both scripts (in perl - yes, would be better done in bourne
shell, I agree) to this mail: the Nick solution is cvsmerge, the
Nick/Mike solution is cvsmerge2.

> Mike Holland  <mike at golden.wattle.id.au>

Thanks to both Nick and Mike for their help.

Pete.
-- 
http://cygnus.uwa.edu.au/~pete/

--
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-------------- next part --------------
#!/usr/bin/perl -w
# Quick Perl script to automate a CVS-style merge utility as described
# by Nick Bannon <nick at it.net.au>. Relies on the RCS utilities ci, co
# and rcsmerge, plus diff, grep and cut. Probably would be more
# wholesome if done as a shell script. :)

use strict;
# merge file name, should probably make it command-line option
my $merge = ".tmpmerge";

# requires two filename params
if (scalar(@ARGV) != 2) { die "$0 <file1> <file2>\n"; }

my $f1 = $ARGV[0];
my $f2 = $ARGV[1];

# grabs the larger line count of the two files.
my $size = &gtr(&lc($f1), &lc($f2));

system("diff -u$size $f1 $f2 | grep '^ ' | cut -c2- > $merge");
system("ci -t-test $merge ; co -l $merge");
system("cp $f1 $merge");
system("ci -mtest1 $merge;co -l $merge");
system("cp $f2 $merge");
system("rcsmerge -r1.1 -r1.2 $merge");

print "Produced file $merge, removing temporary RCS file $merge,v\n";
unlink("$merge,v");

sub gtr {
	my $a = shift;
	my $b = shift;
	if ($a > $b) {
		return $a;
	} else {
		return $b;
	}
}

sub lc {
	my $file = shift;
	my $out = `wc -l $file`;
	$out =~ m/(\d+)/;
	return $1;
}
-------------- next part --------------
#!/usr/bin/perl -w
# Quick Perl script to automate a CVS-style merge utility as described
# by Nick Bannon <nick at it.net.au>. Relies on the utilities merge,
# diff, grep and cut. Probably would be more wholesome if done as a
# shell script. :)

use strict;
# original file name, should probably make it command-line option
my $orig = ".original";

# requires two filename params
if (scalar(@ARGV) != 2) { die "$0 <file1> <file2>\n"; }

my $f1 = $ARGV[0];
my $f2 = $ARGV[1];

# grabs the larger line count of the two files.
my $size = &gtr(&lc($f1), &lc($f2));

system("diff -u$size $f1 $f2 | grep '^ ' | cut -c2- > $orig");
system("merge $f1 $orig $f2");

sub gtr {
	my $a = shift;
	my $b = shift;
	if ($a > $b) {
		return $a;
	} else {
		return $b;
	}
}

sub lc {
	my $file = shift;
	my $out = `wc -l $file`;
	$out =~ m/(\d+)/;
	return $1;
}