Simplify logic for special input functions "and" & "or"

No functional change.

src/input.cpp

@@ -751,19 +751,11 @@ char_event_t inputter_t::read_char(const command_handler_t &command_handler) {
                 }
                 case readline_cmd_t::func_and:
                 case readline_cmd_t::func_or: {
-                    // If previous function has correct status, we keep reading tokens
+                    // If previous function has bad status, we want to skip all functions that
-                    if (evt.get_readline() == readline_cmd_t::func_and) {
+                    // follow us.
-                        // Don't return immediately, we might need to handle it here - like
+                    if ((evt.get_readline() == readline_cmd_t::func_and) != function_status_) {
-                        // self-insert.
+                        drop_leading_readline_events();
-                        if (function_status_) continue;
-                    } else {
-                        if (!function_status_) continue;
                     }
-                    // Else we flush remaining tokens
-                    do {
-                        evt = this->readch();
-                    } while (evt.is_readline());
-                    this->push_front(evt);
                     continue;
                 }
                 default: {

src/input_common.cpp

@@ -285,6 +285,12 @@ void input_event_queue_t::promote_interruptions_to_front() {
     std::rotate(queue_.begin(), first, last);
 }
 
+void input_event_queue_t::drop_leading_readline_events() {
+    queue_.erase(queue_.begin(),
+                 std::find_if(queue_.begin(), queue_.end(),
+                              [](const char_event_t& evt) { return !evt.is_readline(); }));
+}
+
 void input_event_queue_t::prepare_to_select() {}
 void input_event_queue_t::select_interrupted() {}
 void input_event_queue_t::uvar_change_notified() {}

src/input_common.h

@@ -224,6 +224,9 @@ class input_event_queue_t {
         queue_.insert(queue_.begin(), begin, end);
     }
 
+    /// Forget all enqueued readline events in the front of the queue.
+    void drop_leading_readline_events();
+
     /// Override point for when we are about to (potentially) block in select(). The default does
     /// nothing.
     virtual void prepare_to_select();