git svn: lookup new parents correctly from svn:mergeinfo

This appears to be a trivial case where array indices were being
passed to git rev-list, instead of the contents stored in the
array itself.

Signed-off-by: Eric Wong <normalperson@yhbt.net>

git-svn.perl

@@ -3163,7 +3163,8 @@ sub find_extra_svn_parents {
 				next unless $new_parents[$i];
 				next unless $new_parents[$j];
 				my $revs = command_oneline(
-					"rev-list", "-1", "$i..$j",
+					"rev-list", "-1",
+					"$new_parents[$i]..$new_parents[$j]",
 				       );
 				if ( !$revs ) {
 					undef($new_parents[$i]);