svnimport: newer libsvn wants us to ask for the root with "", not "/"

In r27729, libsvn introduced an assert which explicitly
forbids searching the tree at "/". Luckily enough, it
still accepts an empty string "" as the starting point.

http://svn.collab.net/viewvc/svn/trunk/subversion/libsvn_ra/ra_loader.c?r1=27653&r2=27729

Tested against libsvn0-1.5.0-4mdv2009.0 (needs the fix),
libsvn0-1.4.6-5mdv2008.1 (works anyway)
Signed-off-by: NP. Christeas <p_christ@hol.gr>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

contrib/examples/git-svnimport.perl

@@ -933,7 +933,7 @@ sub commit_all {
 	$to_rev = $from_rev + $repack_after;
 	$to_rev = $opt_l if $opt_l < $to_rev;
 	print "Fetching from $from_rev to $to_rev ...\n" if $opt_v;
-	$svn->{'svn'}->get_log("/",$from_rev,$to_rev,0,1,1,\&commit_all);
+	$svn->{'svn'}->get_log("",$from_rev,$to_rev,0,1,1,\&commit_all);
 	my $pid = fork();
 	die "Fork: $!\n" unless defined $pid;
 	unless($pid) {