Add SkipClean option

By default paths are run through the cleanPath method which prevents
using fancier paths like /fetch/http://xkcd.com/534

This adds a SkipClean option so that this path isn't redirected to
/fetch/http/xkcd.com/534

mux.go

@@ -48,6 +48,8 @@ type Router struct {
 	namedRoutes map[string]*Route
 	// See Router.StrictSlash(). This defines the flag for new routes.
 	strictSlash bool
+	// See Router.SkipClean(). This defines the flag for new routes.
+	skipClean bool
 	// If true, do not clear the request context after handling the request
 	KeepContext bool
 }
@@ -73,8 +75,9 @@ func (r *Router) Match(req *http.Request, match *RouteMatch) bool {
 // When there is a match, the route variables can be retrieved calling
 // mux.Vars(request).
 func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
-	// Clean path to canonical form and redirect.
-	if p := cleanPath(req.URL.Path); p != req.URL.Path {
+	if !r.skipClean {
+		// Clean path to canonical form and redirect.
+		if p := cleanPath(req.URL.Path); p != req.URL.Path {
 
 		// Added 3 lines (Philip Schlump) - It was dropping the query string and #whatever from query.
 		// This matches with fix in go 1.2 r.c. 4 for same problem.  Go Issue:
@@ -83,9 +86,10 @@ func (r *Router) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		url.Path = p
 		p = url.String()
 
-		w.Header().Set("Location", p)
-		w.WriteHeader(http.StatusMovedPermanently)
-		return
+			w.Header().Set("Location", p)
+			w.WriteHeader(http.StatusMovedPermanently)
+			return
+		}
 	}
 	var match RouteMatch
 	var handler http.Handler
@@ -133,6 +137,19 @@ func (r *Router) StrictSlash(value bool) *Router {
 	return r
 }
 
+// SkipClean defines the path cleaning behaviour for new routes. The initial
+// value is false.
+//
+// When true, if the route path is "/path//to", it will remain with the double
+// slash. This is helpful if you have a route like: /fetch/http://xkcd.com/534/
+//
+// When false, the path will be cleaned, so /fetch/http://xkcd.com/534/ will
+// become /fetch/http/xkcd.com/534
+func (r *Router) SkipClean(value bool) *Router {
+	r.skipClean = value
+	return r
+}
+
 // ----------------------------------------------------------------------------
 // parentRoute
 // ----------------------------------------------------------------------------
@@ -170,7 +187,7 @@ func (r *Router) buildVars(m map[string]string) map[string]string {
 
 // NewRoute registers an empty route.
 func (r *Router) NewRoute() *Route {
-	route := &Route{parent: r, strictSlash: r.strictSlash}
+	route := &Route{parent: r, strictSlash: r.strictSlash, skipClean: r.skipClean}
 	r.routes = append(r.routes, route)
 	return route
 }
@@ -357,6 +374,7 @@ func cleanPath(p string) string {
 	if p[len(p)-1] == '/' && np != "/" {
 		np += "/"
 	}
+
 	return np
 }