Deprecate public exports in lib/dartdoc.dart. (#3589)

diff --git a/bin/dartdoc.dart b/bin/dartdoc.dart
index 52781d9..1e78f1b 100644
--- a/bin/dartdoc.dart
+++ b/bin/dartdoc.dart
@@ -6,8 +6,11 @@
 
 import 'dart:async';
 
-import 'package:dartdoc/dartdoc.dart';
 import 'package:dartdoc/options.dart';
+import 'package:dartdoc/src/dartdoc.dart';
+import 'package:dartdoc/src/model/model.dart';
+import 'package:dartdoc/src/package_config_provider.dart';
+import 'package:dartdoc/src/package_meta.dart';
 
 /// Analyzes Dart files and generates a representation of included libraries,
 /// classes, and members. Uses the current directory to look for libraries.
diff --git a/lib/dartdoc.dart b/lib/dartdoc.dart
index b4769ec..d7cacc8 100644
--- a/lib/dartdoc.dart
+++ b/lib/dartdoc.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// A documentation generator for Dart.
+@Deprecated('Will be removed in a later version of DartDoc.')
 library dartdoc;
 
 export 'package:dartdoc/src/dartdoc.dart';
diff --git a/lib/options.dart b/lib/options.dart
index 6724c14..6610d83 100644
--- a/lib/options.dart
+++ b/lib/options.dart
@@ -1,7 +1,7 @@
 import 'dart:io' show stderr, exitCode;
 
 import 'package:args/args.dart';
-import 'package:dartdoc/dartdoc.dart' show dartdocVersion, programName;
+import 'package:dartdoc/src/dartdoc.dart' show dartdocVersion, programName;
 import 'package:dartdoc/src/dartdoc_options.dart';
 import 'package:dartdoc/src/generator/generator.dart';
 import 'package:dartdoc/src/logging.dart';
diff --git a/test/end2end/dartdoc_test.dart b/test/end2end/dartdoc_test.dart
index 16ed7ae..7680327 100644
--- a/test/end2end/dartdoc_test.dart
+++ b/test/end2end/dartdoc_test.dart
@@ -7,8 +7,8 @@
 import 'dart:async';
 
 import 'package:analyzer/file_system/file_system.dart';
-import 'package:dartdoc/dartdoc.dart' show Dartdoc, DartdocResults;
 import 'package:dartdoc/options.dart';
+import 'package:dartdoc/src/dartdoc.dart' show Dartdoc, DartdocResults;
 import 'package:dartdoc/src/dartdoc_options.dart';
 import 'package:dartdoc/src/failure.dart';
 import 'package:dartdoc/src/io_utils.dart';
diff --git a/test/html_generator_test.dart b/test/html_generator_test.dart
index 6b37345..93451d8 100644
--- a/test/html_generator_test.dart
+++ b/test/html_generator_test.dart
@@ -4,8 +4,8 @@
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
-import 'package:dartdoc/dartdoc.dart' show DartdocFileWriter;
 import 'package:dartdoc/options.dart';
+import 'package:dartdoc/src/dartdoc.dart' show DartdocFileWriter;
 import 'package:dartdoc/src/dartdoc_options.dart';
 import 'package:dartdoc/src/generator/generator.dart';
 import 'package:dartdoc/src/generator/generator_backend.dart';
diff --git a/test/mustachio/renderers_output_test.dart b/test/mustachio/renderers_output_test.dart
index 1467834..227dea2 100644
--- a/test/mustachio/renderers_output_test.dart
+++ b/test/mustachio/renderers_output_test.dart
@@ -9,8 +9,8 @@
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
-import 'package:dartdoc/dartdoc.dart' show Dartdoc, DartdocFileWriter;
 import 'package:dartdoc/options.dart';
+import 'package:dartdoc/src/dartdoc.dart' show Dartdoc, DartdocFileWriter;
 import 'package:dartdoc/src/dartdoc_options.dart';
 import 'package:dartdoc/src/generator/generator.dart';
 import 'package:dartdoc/src/generator/html_generator.dart';