diff --git a/pkg/nnbd_migration/tool/src/package.dart b/pkg/nnbd_migration/tool/src/package.dart
index 5b484fd4536c..517f874451f0 100644
--- a/pkg/nnbd_migration/tool/src/package.dart
+++ b/pkg/nnbd_migration/tool/src/package.dart
@@ -9,6 +9,24 @@ import 'dart:io';
 
 import 'package:path/path.dart' as path;
 
+/// Return a resolved path including the home directory in place of tilde
+/// references.
+String resolveTildePath(String originalPath) {
+  if (originalPath == null || !originalPath.startsWith('~/')) {
+    return originalPath;
+  }
+
+  String homeDir;
+
+  if (Platform.isWindows) {
+    homeDir = path.absolute(Platform.environment['USERPROFILE']);
+  } else {
+    homeDir = path.absolute(Platform.environment['HOME']);
+  }
+
+  return path.join(homeDir, originalPath.substring(2));
+}
+
 /// Returns the path to the SDK repository this script is a part of.
 final String thisSdkRepo = () {
   var maybeSdkRepoDir = Platform.script.toFilePath();
@@ -24,6 +42,14 @@ final String thisSdkRepo = () {
 
 Uri get thisSdkUri => Uri.file(thisSdkRepo);
 
+/// Abstraction for an unmanaged package.
+class ManualPackage extends Package {
+  ManualPackage(this.packagePath) : super(packagePath);
+
+  @override
+  final String packagePath;
+}
+
 /// Abstraction for a package fetched via Github.
 class GitHubPackage extends Package {
   GitHubPackage(String name, [String label]) : super(name) {
diff --git a/pkg/nnbd_migration/tool/trial_migration.dart b/pkg/nnbd_migration/tool/trial_migration.dart
index 891a1fd1c1ed..93c8d79daf27 100644
--- a/pkg/nnbd_migration/tool/trial_migration.dart
+++ b/pkg/nnbd_migration/tool/trial_migration.dart
@@ -32,6 +32,15 @@ main(List<String> args) async {
       help: 'Select the root of the SDK to analyze against for this run '
           '(compiled with --nnbd).  For example: ../../xcodebuild/DebugX64NNBD/dart-sdk');
 
+  argParser.addMultiOption(
+    'manual_packages',
+    abbr: 'm',
+    defaultsTo: [],
+    help: 'Run migration against packages in these directories.  Does not '
+        'run pub get, any git commands, or any other preparation.',
+    splitCommas: true,
+  );
+
   argParser.addMultiOption(
     'packages',
     abbr: 'p',
@@ -75,9 +84,12 @@ main(List<String> args) async {
   warnOnNoAssertions();
   warnOnNoSdkNnbd(sdk);
 
-  List<Package> packages = (parsedArgs['packages'] as Iterable<String>)
-      .map((n) => SdkPackage(n))
-      .toList(growable: false);
+  List<Package> packages = [
+    for (String package in parsedArgs['packages'] as Iterable<String>)
+      SdkPackage(package),
+    for (String package in parsedArgs['manual_packages'] as Iterable<String>)
+      ManualPackage(package),
+  ];
 
   String categoryOfInterest =
       parsedArgs.rest.isEmpty ? null : parsedArgs.rest.single;