Merge pull request #92: Always use read-object hook during checkout

While refactoring the `CloneVerb` in #77, I moved the `git checkout -f` command to the end of clone, as needed. This is because we will actually fill out blobs during this initial checkout.

However, there was one slight problem: we need the read-object hook. There are two ways to do a checkout in the `GitProcess`, and one was not allowing the read-object hook.

Before #77, this checkout was called before the mount was ready, but that's no longer important.

Thanks @jamill for finding this bug!

Scalar.Common/Git/GitProcess.cs

@@ -413,7 +413,7 @@ public Result CreateBranchWithUpstream(string branchToCreate, string upstreamBra
 
         public Result ForceCheckout(string target)
         {
-            return this.InvokeGitInWorkingDirectoryRoot("checkout -f " + target, useReadObjectHook: false);
+            return this.InvokeGitInWorkingDirectoryRoot("checkout -f " + target, useReadObjectHook: true);
         }
 
         public Result ForceCheckoutAllFiles()

Scalar.FunctionalTests/Tests/EnlistmentPerFixture/CloneTests.cs

@@ -46,6 +46,24 @@ public void CloneWithLocalCachePathWithinSrc()
             result.Output.ShouldContain("'--local-cache-path' cannot be inside the src folder");
         }
 
+        [TestCase]
+        public void SparseCloneWithNoPrefetchSucceeds()
+        {
+            ScalarFunctionalTestEnlistment enlistment = null;
+
+            try
+            {
+                enlistment = ScalarFunctionalTestEnlistment.CloneAndMountWithPerRepoCache(ScalarTestConfig.PathToScalar, skipPrefetch: true);
+
+                ProcessResult result = GitProcess.InvokeProcess(enlistment.RepoRoot, "status");
+                result.ExitCode.ShouldEqual(0, result.Errors);
+            }
+            finally
+            {
+                enlistment?.UnmountAndDeleteAll();
+            }
+        }
+
         [TestCase]
         [Category(Categories.MacOnly)]
         [Category(Categories.NeedsUpdatesForNonVirtualizedMode)]

Scalar/CommandLine/CloneVerb.cs

@@ -624,8 +624,13 @@ private Result CheckoutRepo()
                 }
             }
 
-            if (this.git.ForceCheckout(this.Branch).ExitCodeIsFailure)
+            GitProcess.Result result = this.git.ForceCheckout(this.Branch);
+            if (result.ExitCodeIsFailure)
             {
+                EventMetadata metadata = new EventMetadata();
+                metadata["git-output"] = result.Output;
+                metadata["git-errors"] = result.Errors;
+                this.tracer.RelatedError(metadata, "Failed to checkout repo");
                 return new Result("Failed to checkout repo");
             }