git-svn: path canonicalization uses SVN API

All tests pass with SVN 1.6.  SVN 1.7 remains broken, not worrying
about it yet.

SVN changed its path canonicalization API between 1.6 and 1.7.
http://svnbook.red-bean.com/en/1.6/svn.developer.usingapi.html#svn.developer.usingapi.urlpath
http://svnbook.red-bean.com/en/1.7/svn.developer.usingapi.html#svn.developer.usingapi.urlpath

The SVN API does not accept foo/.. but it also doesn't canonicalize
it.  We have to do it ourselves.

[ew: commit title, fall back if SVN <= 1.6 fails to canonicalize]

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

perl/Git/SVN/Utils.pm

@@ -86,6 +86,30 @@ sub _collapse_dotdot {
 
 
 sub canonicalize_path {
+	my $path = shift;
+	my $rv;
+
+	# The 1.7 way to do it
+	if ( defined &SVN::_Core::svn_dirent_canonicalize ) {
+		$path = _collapse_dotdot($path);
+		$rv = SVN::_Core::svn_dirent_canonicalize($path);
+	}
+	# The 1.6 way to do it
+	# This can return undef on subversion-perl-1.4.2-2.el5 (CentOS 5.2)
+	elsif ( defined &SVN::_Core::svn_path_canonicalize ) {
+		$path = _collapse_dotdot($path);
+		$rv = SVN::_Core::svn_path_canonicalize($path);
+	}
+
+	return $rv if defined $rv;
+
+	# No SVN API canonicalization is available, or the SVN API
+	# didn't return a successful result, do it ourselves
+	return _canonicalize_path_ourselves($path);
+}
+
+
+sub _canonicalize_path_ourselves {
 	my ($path) = @_;
 	my $dot_slash_added = 0;
 	if (substr($path, 0, 1) ne "/") {