Functionality to validate git versions

Author: StanleyGoldman

src/UnityExtension/Assets/Editor/GitHub.Unity/UI/GitPathView.cs

@@ -142,9 +142,24 @@ public override void OnGUI()
 
         private void ValidateAndSetGitInstallPath(string value)
         {
-            Manager.SystemSettings.Set(Constants.GitInstallPathKey, value);
-            Environment.GitExecutablePath = value.ToNPath();
-            gitExecHasChanged = true;
+            GitClient.ValidateGitInstall(value).Then((sucess, result) => {
+                if (!sucess)
+                {
+                    Logger.Trace("Error getting software versions");
+                    return;
+                }
+
+                if (!result.IsValid)
+                {
+                    Logger.Warning("Software versions do not meet minimums Git:{0} GitLfs:{1}", result.GitVersionTask, result.GitLfsVersionTask);
+                    return;
+                }
+
+                Manager.SystemSettings.Set(Constants.GitInstallPathKey, value);
+                Environment.GitExecutablePath = value.ToNPath();
+
+                gitExecHasChanged = true;
+            });
         }
 
         private void MaybeUpdateData()