Adding an E2E test for pack with content during migration.

TestAssets/TestProjects/PJTestLibraryWithConfiguration/contentitem.txt

@@ -0,0 +1 @@
+Random content.

TestAssets/TestProjects/PJTestLibraryWithConfiguration/project.json

@@ -17,5 +17,13 @@
   },
   "frameworks": {
     "netstandard1.5": {}
+  },
+  "packOptions": {
+      "files": {
+          "include": ["contentitem.txt"],
+          "mappings": {
+              "dir/contentitem.txt": "contentitem.txt"
+          }
+      }
   }
 }

test/dotnet-migrate.Tests/GivenThatIWantMigratedAppsToPackContent.cs

@@ -0,0 +1,62 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Build.Construction;
+using Microsoft.DotNet.TestFramework;
+using Microsoft.DotNet.Tools.Common;
+using Microsoft.DotNet.Tools.Test.Utilities;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Xunit;
+using FluentAssertions;
+using System.IO;
+using System.IO.Compression;
+using Microsoft.DotNet.Tools.Migrate;
+using BuildCommand = Microsoft.DotNet.Tools.Test.Utilities.BuildCommand;
+using System.Runtime.Loader;
+using Newtonsoft.Json.Linq;
+
+using MigrateCommand = Microsoft.DotNet.Tools.Migrate.MigrateCommand;
+
+namespace Microsoft.DotNet.Migration.Tests
+{
+    public class GivenThatIWantMigratedAppsToPackContent : TestBase
+    {
+        [Fact]
+        public void ItPacksContentForLibraries()
+        {
+            var projectDirectory = TestAssets
+                .GetProjectJson("PJTestLibraryWithConfiguration")
+                .CreateInstance()
+                .WithSourceFiles()
+                .WithRestoreFiles()
+                .WithEmptyGlobalJson()
+                .Root;
+
+            new TestCommand("dotnet")
+                    .WithForwardingToConsole()
+                    .Execute($"migrate {projectDirectory.FullName}")
+                    .Should()
+                    .Pass();
+
+            var command = new RestoreCommand()
+                .WithWorkingDirectory(projectDirectory)
+                .Execute()
+                .Should()
+                .Pass();
+
+            var result = new PackCommand()
+                .WithWorkingDirectory(projectDirectory)
+                .ExecuteWithCapturedOutput()
+                .Should()
+                .Pass();
+
+            using (var archive = ZipFile.OpenRead(
+                Path.Combine(projectDirectory.FullName, "bin", "debug", "PJTestLibraryWithConfiguration.1.0.0.nupkg")))
+            {
+                archive.Entries.Select(e => e.FullName).Should().Contain("dir/contentitem.txt");
+            }
+        }
+    }
+}