Add real git submodule test

And replace the reflection-based mini test.

Author: AArnott

src/NerdBank.GitVersioning.Tests/NerdBank.GitVersioning.Tests.csproj

@@ -50,13 +50,13 @@
     <Compile Include="GitExtensionsTests.cs" />
     <Compile Include="MSBuildExtensions.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
-    <Compile Include="RepoFinderTests.cs" />
     <Compile Include="RepoTestBase.cs" />
     <Compile Include="SemanticVersionTests.cs" />
     <Compile Include="TestUtilities.cs" />
     <Compile Include="VersionExtensionsTests.cs" />
     <Compile Include="VersionFileTests.cs" />
     <Compile Include="VersionOptionsTests.cs" />
+    <Compile Include="VersionOracleTests.cs" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="..\Nerdbank.GitVersioning.NuGet\build\*.targets">
@@ -83,6 +83,7 @@
     <EmbeddedResource Include="Keys\protectedPair.pfx" />
     <None Include="project.json" />
     <EmbeddedResource Include="test.proj" />
+    <EmbeddedResource Include="repos\submodules.7z" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 

src/NerdBank.GitVersioning.Tests/RepoFinderTests.cs

@@ -1,4 +1,6 @@
-using Validation;
+using SevenZipNET;
+using Validation;
+
 namespace Nerdbank.GitVersioning.Tests
 {
     using System;
@@ -54,5 +56,45 @@ internal static void ExtractEmbeddedResource(string resourcePath, string extract
                 }
             }
         }
+
+        internal static ExpandedRepo ExtractRepoArchive(string repoArchiveName)
+        {
+            string archiveFilePath = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());
+            string expandedFolderPath = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());
+
+            ExtractEmbeddedResource($"repos.{repoArchiveName}.7z", archiveFilePath);
+            try
+            {
+                var extractor = new SevenZipExtractor(archiveFilePath);
+                extractor.ExtractAll(expandedFolderPath);
+                return new ExpandedRepo(expandedFolderPath);
+            }
+            finally
+            {
+                if (File.Exists(archiveFilePath))
+                {
+                    File.Delete(archiveFilePath);
+                }
+            }
+        }
+
+        internal class ExpandedRepo : IDisposable
+        {
+            internal ExpandedRepo(string repoPath)
+            {
+                Requires.NotNullOrEmpty(repoPath, nameof(repoPath));
+                this.RepoPath = repoPath;
+            }
+
+            public string RepoPath { get; private set; }
+
+            public void Dispose()
+            {
+                if (Directory.Exists(this.RepoPath))
+                {
+                    DeleteDirectory(this.RepoPath);
+                }
+            }
+        }
     }
 }

src/NerdBank.GitVersioning.Tests/TestUtilities.cs

@@ -0,0 +1,31 @@
+using System.IO;
+using LibGit2Sharp;
+using Nerdbank.GitVersioning;
+using Nerdbank.GitVersioning.Tests;
+using Xunit;
+using Xunit.Abstractions;
+
+public class VersionOracleTests : RepoTestBase
+{
+    public VersionOracleTests(ITestOutputHelper logger)
+        : base(logger)
+    {
+    }
+
+    [Fact]
+    public void Submodule_RecognizedWithCorrectVersion()
+    {
+        using (var expandedRepo = TestUtilities.ExtractRepoArchive("submodules"))
+        {
+            this.Repo = new Repository(expandedRepo.RepoPath);
+
+            var oracleA = VersionOracle.Create(Path.Combine(expandedRepo.RepoPath, "a"));
+            Assert.Equal("1.3.1", oracleA.SimpleVersion.ToString());
+            Assert.Equal("e238b03e75", oracleA.GitCommitIdShort);
+
+            var oracleB = VersionOracle.Create(Path.Combine(expandedRepo.RepoPath, "b", "projB"));
+            Assert.Equal("2.5.2", oracleB.SimpleVersion.ToString());
+            Assert.Equal("3ea7f010c3", oracleB.GitCommitIdShort);
+        }
+    }
+}

src/NerdBank.GitVersioning.Tests/VersionOracleTests.cs

@@ -1,5 +1,6 @@
 {
   "dependencies": {
+    "7z.NET":  "1.0.3",
     "Microsoft.CodeAnalysis.CSharp": "1.1.1",
     "System.Collections.Immutable": "1.1.37",
     "xunit": "2.1.0",