BUrl: add a Redirect method

* This takes a relative path as a parameter, and modifies the object to
point to the given location.
 * '..' is not handled yet, and will be sent as-is to the server.
 * Makes it possible to follow more types of 302 redirects

In particular, I can now run the tests from Opera's testsuite
(testsuite.opera.com), which shows I have more work to do on cookie
handling.

headers/os/net/Url.h

@@ -29,6 +29,7 @@ public:
 			BUrl&				SetPath(const BString& path);
 			BUrl&				SetRequest(const BString& request);
 			BUrl&				SetFragment(const BString& fragment);
+			void				Redirect(const BString& newLocation);
 			
 	// URL fields access
 			const BString&		UrlString() const;

src/kits/network/libnetapi/Url.cpp

@@ -92,6 +92,42 @@ BUrl::~BUrl()
 // #pragma mark URL fields modifiers
 
 
+void
+BUrl::Redirect(const BString& newLocation)
+{
+	BString oldUrl = UrlString();
+	BUrl newUrl(newLocation);
+
+	if(newUrl.Protocol() != "")
+	{
+		*this = newUrl;
+	} else {
+		// the new location seems to be relative to ours.
+		const BString& newPath = newUrl.Path();
+
+		if(newPath[0] == '/') {
+			// new path is absolute, just adopt it
+			SetPath(newPath);
+		} else {
+			// Path is relative, append it to current one
+			// TODO resolve '..'
+			BString path = Path();
+			// Remove last part of path (the file, if any) so we get the
+			// "current directory"
+			path.Truncate(path.FindLast('/') + 1);
+			path += newPath;
+			SetPath(path);
+		}
+
+		// Also copy request and fragment from the other URL
+		if(newUrl.Request() != "")
+			SetRequest(newUrl.Request());
+		if(newUrl.Fragment() != "")
+			SetRequest(newUrl.Fragment());
+	}
+}
+
+
 BUrl&
 BUrl::SetUrlString(const BString& url)
 {