Add reload capability

This adds a reload button, with shortcut `r`, that reloads the current
page (if any).  This simply re-fetches the content and redraws the page
(which also resets the cursor position).

src/main.rs

@@ -29,10 +29,11 @@ mod history;
 
 const HELP: &str = "Welcome to Asuka Gemini browser!
 
-  Press g to visit an URL
+  Press g to visit a URL
   Press b to go to the previous URL
   Press B to show bookmarks
-  Press a to add current URL to bookmarks
+  Press r to reload
+  Press a to bookmark the current URL
   Press q to exit
 ";
 
@@ -58,6 +59,7 @@ fn main() {
         .button("Back (b)", |s| go_back(s))
         .button("Go To URL (g)", |s| prompt_for_url(s))
         .button("Bookmarks (B)", |s| show_bookmarks(s))
+        .button("Reload (r)", |s| reload_page(s))
         .button("Quit (q)", |s| s.quit())
         .with_id("container"),
     );
@@ -72,6 +74,8 @@ fn main() {
     siv.add_global_callback('B', |s| show_bookmarks(s));
     // pressing b goes to the previous URL if any
     siv.add_global_callback('b', |s| go_back(s));
+    // pressing r reloads the current URL if any
+    siv.add_global_callback('r', |s| reload_page(s));
 
     siv.run();
 }
@@ -164,6 +168,22 @@ fn show_bookmarks(s: &mut Cursive) {
     );
 }
 
+fn reload_page(s: &mut Cursive) {
+    // Get current URL from history and revisit it without modifying history
+    if let Some(url) = history::get_current_url() {
+        match content::get_data(&url) {
+            Ok((meta, new_content)) => {
+                // handle meta header
+                let response = handle_response_status(s, &url, meta, new_content);
+                draw_content(s, &url, response);
+            }
+            Err(msg) => {
+                s.add_layer(Dialog::info(msg));
+            }
+        }
+    }
+}
+
 fn visit_url(s: &mut Cursive, url: &Url) {
     // Close URL popup if any
     if s.find_id::<Dialog>("url_popup").is_some() {