git-svn: use SVN 1.7 to canonicalize when possible

No change on SVN 1.6.  The tests all pass with SVN 1.6 if
canonicalize_url() does nothing, so tests passing doesn't have
much meaning.

The tests are so messed up right now with SVN 1.7 it isn't really
useful to check.  They will be useful later.

[ew: commit title]

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

perl/Git/SVN/Utils.pm

@@ -3,6 +3,8 @@ package Git::SVN::Utils;
 use strict;
 use warnings;
 
+use SVN::Core;
+
 use base qw(Exporter);
 
 our @EXPORT_OK = qw(
@@ -100,6 +102,20 @@ API as a URL.
 =cut
 
 sub canonicalize_url {
+	my $url = shift;
+
+	# The 1.7 way to do it
+	if ( defined &SVN::_Core::svn_uri_canonicalize ) {
+		return SVN::_Core::svn_uri_canonicalize($url);
+	}
+	# There wasn't a 1.6 way to do it, so we do it ourself.
+	else {
+		return _canonicalize_url_ourselves($url);
+	}
+}
+
+
+sub _canonicalize_url_ourselves {
 	my ($url) = @_;
 	$url =~ s#^([^:]+://[^/]*/)(.*)$#$1 . canonicalize_path($2)#e;
 	return $url;