ResetMixedTests: make test more flexible around sparse-checkout

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

Author: derrickstolee

GVFS/GVFS.FunctionalTests/Tests/GitCommands/ResetMixedTests.cs

@@ -85,9 +85,12 @@ public void ResetMixedOnlyAddedThenCheckoutWithConflicts()
             this.ValidateGitCommand("reset --mixed HEAD~1");
 
             // This will reset all the files except the files that were added
-            // and are untracked to make sure we error out with those using sparse-checkout
+            // and are untracked to make sure we error out with those using sparse-checkout.
+            // However, a sparse-checkout-enabled repo uses a different warning
+            // message and leaves the repo in a different state than the control repo.
             this.ValidateGitCommand("checkout -f");
-            this.ValidateGitCommand("checkout " + GitRepoTests.ConflictSourceBranch);
+            this.RunGitCommand("checkout " + GitRepoTests.ConflictSourceBranch, ignoreErrors: true, checkStatus: false);
+            this.ValidateGitCommand("reset --hard");
             this.FilesShouldMatchCheckoutOfTargetBranch();
         }