Ensure workdirPath is not null in Repo.Clone

Author: Ruben Verdoes

LibGit2Sharp.Tests/CloneFixture.cs

@@ -227,5 +227,12 @@ public void CloningAnUrlWithoutPathThrows()
 
             Assert.Throws<InvalidSpecificationException>(() => Repository.Clone("http://github.com", scd.DirectoryPath));
         }
+
+        [Theory]
+        [InlineData("git://github.com/libgit2/TestGitRepository")]
+        public void CloningWithoutWorkdirPathThrows(string url)
+        {
+            Assert.Throws<ArgumentNullException>(() => Repository.Clone(url, null));
+        }
     }
 }

LibGit2Sharp/Repository.cs

@@ -538,6 +538,8 @@ public static string Discover(string startingPath)
         public static string Clone(string sourceUrl, string workdirPath,
             CloneOptions options = null)
         {
+            Ensure.ArgumentNotNull(workdirPath, "workdirPath");
+
             options = options ?? new CloneOptions();
 
             using (GitCheckoutOptsWrapper checkoutOptionsWrapper = new GitCheckoutOptsWrapper(options))