git-svn: SVK merge commits can have >2 parents

From: Alex Vandiver <alex@chmrr.net>
Date: Nov 29, 2009, 07:28 UTC
Message-ID: <1259479636-sup-573@utwig>

  Heya,

While converting a mildly complicated svn repository that was managed with SVK, I ran across the following oddness. `svk smerge` can only merge between _two_ branches at once -- however, the way that svk merge detection works, you can end up with erroneous extra parents from long-dead branches. Case in point:

    export SVKROOT=/tmp/svk-testing-$$
    svk mkdir //trunk -m 'trunk'
    svk mkdir //branches -m 'branches'
    svk co //trunk
    svk cp //trunk/ //branches/feature1 -m 'branch for feature1'
    svk cp //trunk/ //branches/feature2 -m 'branch for feature2'
    svk co //branches/feature1
    cd feature1
    echo "foo" >foo
    svk add foo
    svk ci -m 'feature1 development'
    svk sm //branches/feature1 //trunk -m 'merge feature1 to trunk'
    cd ..
    svk co //branches/feature2
    cd feature2
    echo "bar" >bar
    svk add bar
    svk ci -m 'feature2 development'
    svk sm //trunk //branches/feature2 -m 'merge from trunk'
    cd ..

    git svn clone -s file://$SVKROOT/local

The 'feature2' branch will appear to have three parents: r7, r6, _and_ r5. The r5 parent is extraneous, and only appears because r5 was previously merged into trunk, as part of r6.

Given this, I'm a little confused why find_extra_svk_parents is written the way that it is, in seemingly allowing multiple extra parents to be found. Since the most recent (i.e., highest-numbered) change is by definition the only one that can account for all of the other svk:merge changes, I _believe_ the attached diff to be correct, but I'm unsure because of the implicit current assumption that smerges can produce multiple parents.

 - Alex

-- 
Networking -- only one letter away from not working


From b86b4bb0cecb70d828558b046aa0b3e7b899bf41 Mon Sep 17 00:00:00 2001
From: Alex Vandiver <alex@chmrr.net>
Date: Sun, 29 Nov 2009 02:20:21 -0500
Subject: [PATCH] git-svn: svk merge commits should only add one exta parent

When merging branches based on svk:merge properties, a single merge
can have updated or added multiple svk:merge lines.  If so. only
include the minimal set of new parents.

Signed-off-by: Alex Vandiver <alex@chmrr.net>
---
 git-svn.perl |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/git-svn.perl b/git-svn.perl
index 957d44e..668e50c 100755
--- a/git-svn.perl
+++ b/git-svn.perl
@@ -2940,10 +2940,12 @@ sub find_extra_svk_parents {
 			if ( my $commit = $gs->rev_map_get($rev, $uuid) ) {
 				# wahey!  we found it, but it might be
 				# an old one (!)
-				push @known_parents, $commit;
+				push @known_parents, [ $rev, $commit ];
 			}
 		}
 	}
+	# We only care about the highest-numbered applicable commit
+	@known_parents = map {$_->[1]} sort {$b->[0] <=> $a->[0]} @known_parents;
 	for my $parent ( @known_parents ) {
 		my @cmd = ('rev-list', $parent, map { "^$_" } @$parents );
 		my ($msg_fh, $ctx) = command_output_pipe(@cmd);
@@ -2956,6 +2958,7 @@ sub find_extra_svk_parents {
 			print STDERR
 			    "Found merge parent (svk:merge ticket): $parent\n";
 			push @$parents, $parent;
+			return;
 		}
 	}
 }
-- 
1.6.6.rc0.254.g7352d