fixup! Ensure Tags can be created in detached Head state

Author: nulltoken

LibGit2Sharp.Tests/TagFixture.cs

@@ -234,7 +234,7 @@ public void CreatingATagInAEmptyRepositoryThrows()
 
             using (var repo = new Repository(repoPath))
             {
-                Assert.Throws<LibGit2SharpException>(() => repo.ApplyTag("mynotag"));
+                Assert.Throws<UnbornBranchException>(() => repo.ApplyTag("mynotag"));
             }
         }
 
@@ -246,8 +246,8 @@ public void CreatingATagForHeadInAEmptyRepositoryThrows()
 
             using (var repo = new Repository(repoPath))
             {
-                Assert.Throws<LibGit2SharpException>(() => repo.ApplyTag("mytaghead", "HEAD"));
-                Assert.Throws<LibGit2SharpException>(() => repo.ApplyTag("mytaghead"));
+                Assert.Throws<UnbornBranchException>(() => repo.ApplyTag("mytaghead", "HEAD"));
+                Assert.Throws<UnbornBranchException>(() => repo.ApplyTag("mytaghead"));
             }
         }
 

LibGit2Sharp/Core/Ensure.cs

@@ -209,13 +209,32 @@ public static void ArgumentConformsTo<T>(T argumentValue, Func<T, bool> checker,
         }
 
         public static void GitObjectIsNotNull(GitObject gitObject, string identifier)
+        {
+            Func<string, LibGit2SharpException> exceptionBuilder;
+
+            if (string.Equals("HEAD", identifier, StringComparison.Ordinal))
+            {
+                exceptionBuilder = m => new UnbornBranchException(m);
+            }
+            else
+            {
+                exceptionBuilder = m => new LibGit2SharpException(m);
+            }
+
+            GitObjectIsNotNull(gitObject, identifier, exceptionBuilder);
+        }
+
+        public static void GitObjectIsNotNull(
+            GitObject gitObject,
+            string identifier,
+            Func<string, LibGit2SharpException> exceptionBuilder)
         {
             if (gitObject != null)
             {
                 return;
             }
 
-            throw new LibGit2SharpException(string.Format(CultureInfo.InvariantCulture,
+            throw exceptionBuilder(string.Format(CultureInfo.InvariantCulture,
                                                      "No valid git object identified by '{0}' exists in the repository.",
                                                      identifier));
         }

LibGit2Sharp/RepositoryExtensions.cs

@@ -68,7 +68,7 @@ private static void EnsureNoGitLink<T>() where T : GitObject
         /// <param name="tagName">The name of the tag to create.</param>
         public static Tag ApplyTag(this IRepository repository, string tagName)
         {
-            return ApplyTag(repository, tagName, RetrieveHeadCommitId(repository, "Cannot apply Tag.").Sha);
+            return repository.Tags.Add(tagName, RetrieveHeadCommit(repository));
         }
 
         /// <summary>
@@ -91,16 +91,16 @@ public static Tag ApplyTag(this IRepository repository, string tagName, string o
         /// <param name="message">The annotation message.</param>
         public static Tag ApplyTag(this IRepository repository, string tagName, Signature tagger, string message)
         {
-            return ApplyTag(repository, tagName, RetrieveHeadCommitId(repository, "Cannot apply Tag.").Sha, tagger, message);
+            return repository.Tags.Add(tagName, RetrieveHeadCommit(repository), tagger, message);
         }
 
-        private static ObjectId RetrieveHeadCommitId(IRepository repository, string message)
+        private static Commit RetrieveHeadCommit(IRepository repository)
         {
             Commit commit = repository.Head.Tip;
 
-            Ensure.GitObjectIsNotNull(commit, "HEAD");
+            Ensure.GitObjectIsNotNull(commit, "HEAD", m => new UnbornBranchException(m));
 
-            return commit.Id;
+            return commit;
         }
 
         /// <summary>