cache git collections with lazy initialization

Replaces direct instantiations of Tags, Branches, Commits, Remotes, and References with lazy initialization. This avoids redundant object creation and improves performance by deferring instantiation until the collection is accessed.

Author: arturcic

src/GitVersion.LibGit2Sharp/Git/GitRepository.cs

@@ -23,11 +23,20 @@ private IRepository RepositoryInstance
     public bool IsShallow => RepositoryInstance.Info.IsShallow;
     public IBranch Head => this.repositoryCache.GetOrWrap(RepositoryInstance.Head, RepositoryInstance.Diff);
 
-    public ITagCollection Tags => new TagCollection(RepositoryInstance.Tags, RepositoryInstance.Diff, this.repositoryCache);
-    public IBranchCollection Branches => new BranchCollection(RepositoryInstance.Branches, RepositoryInstance.Diff, this.repositoryCache);
-    public ICommitCollection Commits => new CommitCollection(RepositoryInstance.Commits, RepositoryInstance.Diff, this.repositoryCache);
-    public IRemoteCollection Remotes => new RemoteCollection(RepositoryInstance.Network.Remotes, this.repositoryCache);
-    public IReferenceCollection References => new ReferenceCollection(RepositoryInstance.Refs, this.repositoryCache);
+    private ITagCollection? tags;
+    public ITagCollection Tags => this.tags ??= new TagCollection(RepositoryInstance.Tags, RepositoryInstance.Diff, this.repositoryCache);
+
+    private IBranchCollection? branches;
+    public IBranchCollection Branches => this.branches ??= new BranchCollection(RepositoryInstance.Branches, RepositoryInstance.Diff, this.repositoryCache);
+
+    private ICommitCollection? commits;
+    public ICommitCollection Commits => this.commits ??= new CommitCollection(RepositoryInstance.Commits, RepositoryInstance.Diff, this.repositoryCache);
+
+    private IRemoteCollection? remotes;
+    public IRemoteCollection Remotes => this.remotes ??= new RemoteCollection(RepositoryInstance.Network.Remotes, this.repositoryCache);
+
+    private IReferenceCollection? references;
+    public IReferenceCollection References => this.references ??= new ReferenceCollection(RepositoryInstance.Refs, this.repositoryCache);
 
     public void DiscoverRepository(string? gitDirectory)
     {