Implement xmpp: URI passing from the CLI

When receiving such an argument, open a new Tab.

This partially reverts commit 690e7113ab.

src/main.rs

@@ -76,9 +76,26 @@ fn main() {
 
     let app = adw::Application::builder()
         .application_id("fr.linkmauve.XmppClient")
+        .flags(gio::ApplicationFlags::HANDLES_COMMAND_LINE)
         .build();
 
-    app.connect_activate(move |app| {
+    app.connect_command_line(move |app, command_line| {
+        let args = command_line.arguments();
+        let mut iter = args.iter();
+        iter.next().unwrap();
+        let win = app.active_window().unwrap();
+        let win: &window::MainWindow = win.downcast_ref().unwrap();
+        for arg in iter {
+            let arg = arg.to_str().unwrap().to_owned();
+            if let Some(jid) = arg.strip_prefix("xmpp:") {
+                let tab = Tab::new(jid, jid);
+                win.tabs_store().append(&tab);
+            }
+        }
+        0
+    });
+
+    app.connect_startup(move |app| {
         let win = window::MainWindow::new(app);
 
         let action_close = gio::ActionEntry::builder("close")