GitRepoTests: move extra setup into CreateEnlistment()

Some subclasses of GitRepoTests override CreateEnlistment so they can do
extra steps after the base class creates the repo. However, those steps
happen between the base CreateEnlistment() and the rest of the TestSetup
code.

This started failing with the v2.28.0 upgrade because 'git status'
started reporting new info about sparse-checkouts.

Move the sparse-checkout setup code into CreateEnlistment() to stop
failures.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

Author: derrickstolee

Scalar.FunctionalTests/Tests/GitCommands/GitRepoTests.cs

@@ -132,26 +132,6 @@ public virtual void SetupForTest()
                 this.CreateEnlistment();
             }
 
-            if (this.validateWorkingTree == Settings.ValidateWorkingTreeMode.SparseMode)
-            {
-                StringBuilder sb = new StringBuilder();
-
-                foreach (string folder in SparseModeFolders)
-                {
-                    sb.Append(folder.Replace(Path.DirectorySeparatorChar, TestConstants.GitPathSeparator)
-                                    .Trim(TestConstants.GitPathSeparator));
-                    sb.Append("\n");
-                }
-
-                GitProcess.InvokeProcess(this.ControlGitRepo.RootPath, "sparse-checkout init --cone", string.Empty);
-                GitProcess.InvokeProcess(this.ControlGitRepo.RootPath, "sparse-checkout set --stdin", sb.ToString());
-
-                // This line shouldn't be necessary!
-                GitProcess.InvokeProcess(this.Enlistment.RepoRoot, "sparse-checkout init --cone", string.Empty);
-                GitProcess.InvokeProcess(this.Enlistment.RepoRoot, "sparse-checkout set --stdin", sb.ToString());
-                this.pathPrefixes = SparseModeFolders;
-            }
-
             this.ValidateGitCommand("checkout " + this.ControlGitRepo.Commitish);
 
             this.CheckHeadCommitTree();
@@ -221,6 +201,26 @@ protected void CreateEnlistment(string commitish = null)
             GitProcess.Invoke(this.Enlistment.RepoRoot, "config advice.statusUoption false");
             this.ControlGitRepo = ControlGitRepo.Create(commitish);
             this.ControlGitRepo.Initialize();
+
+            if (this.validateWorkingTree == Settings.ValidateWorkingTreeMode.SparseMode)
+            {
+                StringBuilder sb = new StringBuilder();
+
+                foreach (string folder in SparseModeFolders)
+                {
+                    sb.Append(folder.Replace(Path.DirectorySeparatorChar, TestConstants.GitPathSeparator)
+                                    .Trim(TestConstants.GitPathSeparator));
+                    sb.Append("\n");
+                }
+
+                GitProcess.InvokeProcess(this.ControlGitRepo.RootPath, "sparse-checkout init --cone", string.Empty);
+                GitProcess.InvokeProcess(this.ControlGitRepo.RootPath, "sparse-checkout set --stdin", sb.ToString());
+
+                // This line shouldn't be necessary!
+                GitProcess.InvokeProcess(this.Enlistment.RepoRoot, "sparse-checkout init --cone", string.Empty);
+                GitProcess.InvokeProcess(this.Enlistment.RepoRoot, "sparse-checkout set --stdin", sb.ToString());
+                this.pathPrefixes = SparseModeFolders;
+            }
         }
 
         protected virtual void DeleteEnlistment()