Fix Code Format warning

Author: HHobeck

src/GitVersion.Core.Tests/Core/RepositoryStoreTests.cs

@@ -209,7 +209,7 @@ public void GetBranchesContainingCommitThrowsDirectlyOnNullCommit()
         var fixtureRepository = fixture.Repository.ToGitRepository();
         var gitRepoMetadataProvider = new RepositoryStore(this.log, fixtureRepository);
 
-        Assert.Throws<ArgumentNullException>(() => gitRepoMetadataProvider.GetBranchesContainingCommit(null));
+        Assert.Throws<ArgumentNullException>(() => gitRepoMetadataProvider.GetBranchesContainingCommit(null!));
     }
 
     [Test]

src/GitVersion.Core/Core/RepositoryStore.cs

@@ -147,6 +147,8 @@ private static bool IsReleaseBranch(INamedReference branch, IEnumerable<KeyValue
 
     public IEnumerable<IBranch> GetBranchesContainingCommit(ICommit commit, IEnumerable<IBranch>? branches = null, bool onlyTrackedBranches = false)
     {
+        commit.NotNull();
+
         var branchesContainingCommitFinder = new BranchesContainingCommitFinder(this.repository, this.log);
         return branchesContainingCommitFinder.GetBranchesContainingCommit(commit, branches, onlyTrackedBranches);
     }