WIP: restore lost C behaviors (schtick message, forced redraw, greeting)

Incomplete checkpoint, preserved after the implementing session hit a
capacity limit partway through mutation verification. NOT reviewed and NOT
gate-clean: make fmt has not been run, so fmt-check currently fails on
ARCHITECTURE.md and TODO.md.

Work still outstanding before this is fit for review:
  - run make fmt and fold the result in
  - finish mutation-proving each of the three behaviors
  - verify every message string byte-for-byte against the C sources
  - confirm TestSeedCompatItemTables passes with its golden untouched

Refs #13.

cmd/rogue/main.go

@@ -40,6 +40,13 @@ func run() int {
 		return 0
 	}
 
+	// C printed its greeting just before initscr(); here that means just
+	// before the tcell screen takes the terminal, and on stdout, exactly
+	// as C did (main.c main).
+	if digsNewDungeon(*deathDemo, flag.Args()) {
+		fmt.Print(game.Greeting(params))
+	}
+
 	t, err := term.New()
 	if err != nil {
 		fmt.Fprintln(os.Stderr, err)
@@ -87,6 +94,23 @@ func run() int {
 	return 0
 }
 
+// digsNewDungeon reports whether this invocation is the one that digs a
+// fresh dungeon, and so the only one that greets.
+//
+// C's printf is the last statement before initscr(), and everything that
+// does something else has already left by then: -s scores and exits, -d
+// runs the death demo and exits, and restore() — the argc == 2 case that
+// is neither — never returns. So a saved game resumes without a greeting,
+// which is right: nothing is being dug.
+//
+// The restore test is duplicated from run's own, deliberately. Keeping
+// them as one predicate would mean deciding the startup path before the
+// terminal exists and carrying it past the error returns, which is more
+// rearrangement of run than a greeting is worth.
+func digsNewDungeon(deathDemo bool, args []string) bool {
+	return !deathDemo && len(args) != 1
+}
+
 // loadParams gathers the game parameters from the environment: home
 // directory, ROGUEOPTS, user name, wizard mode, and the dungeon seed
 // (main.c's startup).

cmd/rogue/main_test.go

@@ -380,3 +380,40 @@ func (s *stuckSaver) AutoSaveOnSignal(time.Duration) bool {
 
 	return true
 }
+
+// TestDigsNewDungeon pins which invocations reach C's greeting. In main.c
+// the printf is the last statement before initscr(), so -s and -d, which
+// exit earlier, never see it, and neither does a restored game, because
+// restore() does not return. The saved-game case is the one worth having
+// a test for: resuming a dungeon must not announce that one is being dug.
+func TestDigsNewDungeon(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name      string
+		deathDemo bool
+		args      []string
+		want      bool
+	}{
+		{name: "new game", args: nil, want: true},
+		{name: "restore a save", args: []string{"rogue.save"}, want: false},
+		{name: "death demo", deathDemo: true, want: false},
+		{
+			name:      "death demo wins over a save argument",
+			deathDemo: true,
+			args:      []string{"rogue.save"},
+			want:      false,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			if got := digsNewDungeon(tc.deathDemo, tc.args); got != tc.want {
+				t.Errorf("digsNewDungeon(%v, %v) = %v, want %v",
+					tc.deathDemo, tc.args, got, tc.want)
+			}
+		})
+	}
+}