golink: ignore hyphens and allow changing name

- ignore hyphens, preventing link ambiguity. If hyphens are included
  when creating the link, they are saved as the "canonical" name for
  the link, but links are still resolved without them.

- allow overwriting the "canonical" name for a short link by simply
  recreating it with the new canonical name. Stats are not updated when
  the canonical name is updated, which is probably fine.

Change-Id: Ia962caa846489850784ef15cdfad7f13bafd8842

golink.go

@@ -148,6 +148,7 @@ http://go/<input name=short size=20 value="{{.Short}}"> ==&gt; <input name=long
 
 func linkPath(short string) string {
 	name := url.PathEscape(strings.ToLower(short))
+	name = strings.ReplaceAll(name, "-", "")
 	name = strings.ReplaceAll(name, ".", "%2e")
 	return filepath.Join(*linkDir, name)
 }
@@ -302,6 +303,7 @@ func serveSave(w http.ResponseWriter, r *http.Request) {
 			Created: now,
 		}
 	}
+	dl.Short = short
 	dl.Long = long
 	dl.LastEdit = now
 	dl.Owner = login