Add a preferences window

This adds a preference window with default preferences to change the
sparkle options and to set a custom path to a git binary.

PBNSURLPathUserDefaultsTransfomer.m

@@ -0,0 +1,46 @@
+//
+//  PBNSURLPathUserDefaultsTransfomer.m
+//  GitX
+//
+//  Created by Christian Jacobsen on 28/09/2008.
+//  Copyright 2008 __MyCompanyName__. All rights reserved.
+//
+
+#import "PBNSURLPathUserDefaultsTransfomer.h"
+
+/*
+ This ValueTransformer is used to store NSURLs in the user defaults system
+ as strings, without a host part. It is assumed that the path is an absolute
+ path in the local filesystem.
+*/
+
+@implementation PBNSURLPathUserDefaultsTransfomer
+
++ (Class)transformedValueClass {
+	return [NSURL class];
+}
+
++ (BOOL)allowsReverseTransformation {
+	return YES;
+}
+
+- (id)transformedValue:(id)value {
+	if(value == nil)
+	{
+		return nil;
+	}
+
+	return [NSURL URLWithString:value
+				  relativeToURL:[NSURL URLWithString:@"file://localhost/"]];
+}
+
+- (id)reverseTransformedValue:(id)value {
+	if(value == nil)
+	{
+		return nil;
+	}
+
+	return [value path];
+}
+
+@end