Test SetConfigSearchPaths for empty string/array.

Adds testing to verify that passing an empty string or array to
SetConfigSearchPaths should reset the search path to the default just as null
does.

Author: Ryan Roden-Corrent

LibGit2Sharp.Tests/ConfigurationFixture.cs

@@ -452,19 +452,35 @@ public void CanSetAndGetMultipleSearchPaths()
         [Fact]
         public void CanResetSearchPaths()
         {
-            // set the global search path to its default value
+            // all of these calls should reset the config path to the default
+            Action[] resetActions =
+            {
+                () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global),
+                () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null),
+                () => GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, string.Empty),
+            };
+
+            // record the default search path
             GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null);
             var oldPaths = GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global);
             Assert.NotNull(oldPaths);
 
-            // change to something other than the default
+            // generate a non-default path to set
             var newPaths = new string[] { Path.Combine(Constants.TemporaryReposPath, Path.GetRandomFileName()) };
-            GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, newPaths);
-            Assert.Equal(newPaths, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global));
 
-            // set it back to the default
+            foreach (var tryToReset in resetActions)
+            {
+                // change to the non-default path
+                GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, newPaths);
+                Assert.Equal(newPaths, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global));
+
+                // set it back to the default
+                tryToReset();
+                Assert.Equal(oldPaths, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global));
+            }
+
+            // make sure the config paths are reset after the test ends
             GlobalSettings.SetConfigSearchPaths(ConfigurationLevel.Global, null);
-            Assert.Equal(oldPaths, GlobalSettings.GetConfigSearchPaths(ConfigurationLevel.Global));
         }
 
         [Fact]