[LibGit2Sharp] Proposal for #161 fix

issue-161.patch

 LibGit2Sharp.Tests/ConfigurationFixture.cs |   38 ++++++++++++++++++++++++++-
 LibGit2Sharp/Configuration.cs              |   36 +++++++++++++++++++-------
 LibGit2Sharp/Core/Ensure.cs                |   22 +++++++++++----
 3 files changed, 78 insertions(+), 18 deletions(-)

diff --git a/LibGit2Sharp.Tests/ConfigurationFixture.cs b/LibGit2Sharp.Tests/ConfigurationFixture.cs
index 7e1ebd9..634ed21 100644
--- a/LibGit2Sharp.Tests/ConfigurationFixture.cs
+++ b/LibGit2Sharp.Tests/ConfigurationFixture.cs
@@ -1,6 +1,6 @@
 using System;
 using System.IO;
-using System.Text.RegularExpressions;
+using System.Text;
 using LibGit2Sharp.Tests.TestHelpers;
 using Xunit;
 
@@ -44,7 +44,7 @@ private static void AssertValueInGlobalConfigFile(string regex)
         }
 
         [Fact]
-        public void CanDeleteConfiguration()
+        public void CanDeleteAnEntryFromTheLocalConfiguration()
         {
             var path = BuildTemporaryCloneOfTestRepo(StandardTestRepoPath);
             using (var repo = new Repository(path.RepositoryPath))
@@ -60,6 +60,40 @@ public void CanDeleteConfiguration()
             }
         }
 
+        [Fact]
+        public void CanDeleteAnEntryFromTheGlobalConfiguration()
+        {
+            SelfCleaningDirectory scd = BuildSelfCleaningDirectory();
+
+            string confs = Path.Combine(scd.DirectoryPath, "confs");
+            Directory.CreateDirectory(confs);
+
+            string globalLocation = Path.Combine(confs, "my-global-config");
+
+            StringBuilder sb = new StringBuilder()
+                .AppendLine("[Wow]")
+                .AppendFormat("Man-I-am-totally-global = 42{0}", Environment.NewLine);
+
+            File.WriteAllText(globalLocation, sb.ToString());
+
+            var options = new RepositoryOptions
+            {
+                GlobalConfigurationLocation = globalLocation,
+            };
+
+            using (var repo = new Repository(BareTestRepoPath, options))
+            {
+                Assert.True(repo.Config.HasGlobalConfig);
+                Assert.Equal(42, repo.Config.Get<int>("Wow.Man-I-am-totally-global", 1337));
+
+                repo.Config.Delete("Wow.Man-I-am-totally-global");
+                Assert.Equal(42, repo.Config.Get<int>("Wow.Man-I-am-totally-global", 1337));
+
+                repo.Config.Delete("Wow.Man-I-am-totally-global", ConfigurationLevel.Global);
+                Assert.Equal(1337, repo.Config.Get<int>("Wow.Man-I-am-totally-global", 1337));
+            }
+        }
+
         [SkippableFact]
         public void CanGetGlobalStringValue()
         {
diff --git a/LibGit2Sharp/Configuration.cs b/LibGit2Sharp/Configuration.cs
index 8784b43..fa2d978 100644
--- a/LibGit2Sharp/Configuration.cs
+++ b/LibGit2Sharp/Configuration.cs
@@ -142,9 +142,19 @@ public void Dispose()
         ///   Delete a configuration variable (key and value).
         /// </summary>
         /// <param name = "key">The key to delete.</param>
-        public void Delete(string key)
+        /// <param name = "level">The configuration file which should be considered as the target of this operation</param>
+        public void Delete(string key, ConfigurationLevel level = ConfigurationLevel.Local)
         {
-            Ensure.Success(NativeMethods.git_config_delete(localHandle, key));
+            ConfigurationSafeHandle h = RetrieveConfigurationHandle(level);
+
+            int res = NativeMethods.git_config_delete(h, key);
+
+            if (res == (int)GitErrorCode.GIT_ENOTFOUND)
+            {
+                return;
+            }
+
+            Ensure.Success(res);
             Save();
         }
 
@@ -314,6 +324,19 @@ public void Set<T>(string key, T value, ConfigurationLevel level = Configuration
         {
             Ensure.ArgumentNotNullOrEmptyString(key, "key");
 
+            ConfigurationSafeHandle h = RetrieveConfigurationHandle(level);
+
+            if (!configurationTypedUpdater.ContainsKey(typeof(T)))
+            {
+                throw new ArgumentException(string.Format(CultureInfo.InvariantCulture, "Generic Argument of type '{0}' is not supported.", typeof(T).FullName));
+            }
+
+            configurationTypedUpdater[typeof(T)](key, value, h);
+            Save();
+        }
+
+        private ConfigurationSafeHandle RetrieveConfigurationHandle(ConfigurationLevel level)
+        {
             if (level == ConfigurationLevel.Local && !HasLocalConfig)
             {
                 throw new LibGit2Exception("No local configuration file has been found. You must use ConfigurationLevel.Global when accessing configuration outside of repository.");
@@ -348,14 +371,7 @@ public void Set<T>(string key, T value, ConfigurationLevel level = Configuration
                 default:
                     throw new ArgumentException(string.Format(CultureInfo.InvariantCulture, "Configuration level has an unexpected value ('{0}').", Enum.GetName(typeof(ConfigurationLevel), level)), "level");
             }
-
-            if (!configurationTypedUpdater.ContainsKey(typeof(T)))
-            {
-                throw new ArgumentException(string.Format(CultureInfo.InvariantCulture, "Generic Argument of type '{0}' is not supported.", typeof(T).FullName));
-            }
-
-            configurationTypedUpdater[typeof(T)](key, value, h);
-            Save();
+            return h;
         }
 
         private delegate int ConfigGetter<T>(out T value, ConfigurationSafeHandle handle, string name);
diff --git a/LibGit2Sharp/Core/Ensure.cs b/LibGit2Sharp/Core/Ensure.cs
index 60566d3..f80651e 100644
--- a/LibGit2Sharp/Core/Ensure.cs
+++ b/LibGit2Sharp/Core/Ensure.cs
@@ -64,16 +64,26 @@ public static void Success(int result, bool allowPositiveResult = false)
                 return;
             }
 
+            string errorMessage;
             GitError error = NativeMethods.giterr_last().MarshalAsGitError();
 
-            var errorMessage = (string)marshaler.MarshalNativeToManaged(error.Message);
+
+            if (error == null)
+            {
+                error = new GitError { Klass = -1, Message = IntPtr.Zero };
+                errorMessage = "No error message has been provided by the native library";
+            }
+            else
+            {
+                errorMessage = (string)marshaler.MarshalNativeToManaged(error.Message);
+            }
 
             throw new LibGit2Exception(
-                String.Format(CultureInfo.InvariantCulture, "An error was raised by libgit2. Class = {0} ({1}).{2}{3}",
-                              Enum.GetName(typeof(GitErrorType), error.Klass),
-                              result,
-                              Environment.NewLine,
-                              errorMessage));
+                    String.Format(CultureInfo.InvariantCulture, "An error was raised by libgit2. Class = {0} ({1}).{2}{3}",
+                                  Enum.GetName(typeof(GitErrorType), error.Klass),
+                                  result,
+                                  Environment.NewLine,
+                                  errorMessage));
         }
 
         /// <summary>
-- 
1.7.8.msysgit.0