hoa: output "unambiguous" only for non-deterministic automata by default

* src/twaalgos/hoa.cc: Output do not output "unambiguous" if the
automaton is deterministic.  Add option "v" to cancel this restriction,
and also output "no-univ-branch".
* src/twaalgos/hoa.hh: Document the "v" option.
* src/tests/readsave.test: Test it.
* src/tests/unambig.test: Adjust for unambiguous not being output
if the automaton is deterministic.
* src/bin/common_aoutput.cc, NEWS: Document it.
* doc/org/hoa.org: Add a summary table about how properties are handled.
* src/twa/twa.hh (prop_deterministic): Setting this should also
set the unambiguous property.
* src/twaalgos/isunamb.cc: Simplify the property check.

src/twaalgos/hoa.cc

@@ -243,6 +243,7 @@ namespace spot
     bool newline = true;
     hoa_acceptance acceptance = Hoa_Acceptance_States;
     bool implicit_labels = false;
+    bool verbose = false;
 
     if (opt)
       while (*opt)
@@ -264,6 +265,9 @@ namespace spot
 	    case 't':
 	      acceptance = Hoa_Acceptance_Transitions;
 	      break;
+	    case 'v':
+	      verbose = true;
+	      break;
 	    default:
 	      throw std::runtime_error
 		(std::string("unknown option for print_hoa(): ") + c);
@@ -387,6 +391,13 @@ namespace spot
 	  }
 	os << str;
       };
+    // We do not support alternating automata so far, and it's
+    // probable that nobody cares about the "no-univ-branch"
+    // properties.  The "univ-branch" properties seems more important
+    // to announce that the automaton might not be parsable by tools
+    // that do not support alternating automata.
+    if (verbose)
+      prop(" no-univ-branch");
     implicit_labels = md.use_implicit_labels;
     if (implicit_labels)
       prop(" implicit-labels");
@@ -402,7 +413,12 @@ namespace spot
       prop(" complete");
     if (md.is_deterministic)
       prop(" deterministic");
-    if (aut->prop_unambiguous())
+    // Deterministic automata are also unambiguous, so writing both
+    // properties seems redundant.  People working on unambiguous
+    // automata are usually concerned about non-deterministic
+    // unambiguous automata.  So do not mention "unambiguous"
+    // in the case of deterministic automata.
+    if (aut->prop_unambiguous() && (verbose || !md.is_deterministic))
       prop(" unambiguous");
     assert(!(aut->prop_stutter_invariant() && aut->prop_stutter_sensitive()));
     if (aut->prop_stutter_invariant())

src/twaalgos/hoa.hh

@@ -34,7 +34,7 @@ namespace spot
   ///        option: (i) implicit labels for complete and
   ///        deterministic automata, (s) state-based acceptance, (t)
   ///        transition-based acceptance, (m) mixed acceptance, (l)
-  ///        single-line output.
+  ///        single-line output, (v) verbose properties.
   SPOT_API std::ostream&
   print_hoa(std::ostream& os,
 	    const const_twa_ptr& g,

src/twaalgos/isunamb.cc

@@ -27,7 +27,7 @@ namespace spot
 {
   bool is_unambiguous(const const_twa_graph_ptr& aut)
   {
-    if (aut->prop_deterministic() || aut->prop_unambiguous())
+    if (aut->prop_unambiguous())
       return true;
     auto clean_a = scc_filter_states(aut);
     if (clean_a->num_edges() == 0)