acquisition: drive a DataSource from the registry; --source and --source-opt

src/main.cpp

@@ -7,6 +7,7 @@
 #include "waveform.hpp"
 #include "model.hpp"
 #include "plot_host.hpp"
+#include "source/registry.hpp"
 #include "source_dialog.hpp"
 #include "ui.hpp"
 
@@ -18,6 +19,7 @@
 int main(int argc, char** argv) {
   udpscope::Config cfg;
   try {
+    udpscope::register_builtin_sources();
     cfg = udpscope::parse_args(argc, argv);
     // The preferences fill in what the command line did not decide. `--relative-time` is an explicit
     // instruction for this run, so a preference can only turn the mode on, never off -- which is also
@@ -57,13 +59,13 @@ int main(int argc, char** argv) {
   // declining must cost no buffer and no socket, and nothing below has to cope with "no source".
   // `--open` is the other answer to that question, and the chooser knows it: its Waveforms page
   // fills `open_waveform` in instead of the connection fields.
-  const bool asked = !cfg.server_specified && cfg.open_waveform.empty();
+  const bool asked = !cfg.has_source() && cfg.open_waveform.empty();
   if (asked && !udpscope::choose_source(cfg)) return 0;
   // A source named on the command line skips the chooser, but its *stored* configuration still
   // applies: the buffer size, the clock and the capture ring are decided here, before the model --
   // which is the only moment they can be -- and a saved host whose buffer was ignored because the
   // address came from the command line is an edit that looks like it never took effect.
-  if (cfg.server_specified) udpscope::apply_stored_settings(cfg);
+  if (cfg.has_source()) udpscope::apply_stored_settings(cfg);
 
   // Everything from here to `gtk_window_present()` inside `run_ui()` runs with no main loop: the
   // buffer is allocated, a recording is read, then the whole UI is built. The chooser's window is