Implement support for NO_COLOR/FORCE_COLOR env with isatty and journald checks for autodetection.

tests/test_cli.py

@@ -76,8 +76,10 @@ def test_extra_import_paths_ignores_other_python_versions(tmp_path, monkeypatch)
         assert str(other_site) not in sys.path
 
 
-def test_cli_snapshot_line_format(tmp_path, capsys):
+def test_cli_snapshot_line_format(tmp_path, capsys, monkeypatch):
     """Snapshot lines are timestamped and colored with metadata."""
+    monkeypatch.setenv("FORCE_COLOR", "1")
+    monkeypatch.delenv("NO_COLOR", raising=False)
     path = tmp_path / "test.kantadb"
     ts = datetime(2026, 8, 12, 10, 6, 52, 375398, tzinfo=UTC)
     mtime = datetime(2026, 8, 12, 9, 0, 0, tzinfo=UTC)
@@ -105,6 +107,30 @@ def test_cli_snapshot_line_format(tmp_path, capsys):
     assert "\x1b[38;5;242m 13 B" in err
 
 
+def test_cli_strips_ansi_without_color_support(tmp_path, capsys, monkeypatch):
+    """Without a tty and with NO_COLOR set, output contains no ANSI codes."""
+    monkeypatch.setenv("NO_COLOR", "1")
+    monkeypatch.delenv("FORCE_COLOR", raising=False)
+    path = tmp_path / "test.kantadb"
+    ts = datetime(2026, 8, 12, 10, 6, 52, 375398, tzinfo=UTC)
+    serializer = JsonSerializer()
+    framer = LineFramer()
+
+    snapshot = Snapshot(ts=ts, v=1, m=None, state={"counter": 5})
+    change = ChangeRecord(ts=ts, a="inc", v=1, u="user1", diff={"counter": 6})
+    data = framer.frame_snapshot(
+        serializer.encode(snapshot), record_offset=0
+    ) + framer.frame_change(serializer.encode(change), record_offset=0)
+    path.write_bytes(data)
+
+    code = main([str(path)])
+    assert code == 0
+
+    err = capsys.readouterr().err
+    assert "\x1b[" not in err
+    assert "snapshot s0" in err
+
+
 def test_import_dotted_from_file_path(tmp_path):
     """--data can be a filesystem path with an optional colon-separated symbol."""
     module = tmp_path / "models.py"