Ensure IEquatable takes nullable type

.editorconfig

@@ -178,3 +178,6 @@ dotnet_diagnostic.CA1810.severity = warning
 
 # CA1816: Dispose methods should call SuppressFinalize
 dotnet_diagnostic.CA1816.severity = warning
+
+# IDE0005: Using directive is unnecessary.
+dotnet_diagnostic.IDE0005.severity = warning

src/GitVersion.Core/Configuration/ConfigFileLocator.cs

@@ -20,9 +20,9 @@ public ConfigFileLocator(IFileSystem fileSystem, IOptions<GitVersionOptions> opt
 
         public string FilePath { get; }
 
-        public bool HasConfigFileAt(string? workingDirectory) => this.fileSystem.Exists(Path.Combine(workingDirectory, FilePath));
+        public bool HasConfigFileAt(string workingDirectory) => this.fileSystem.Exists(Path.Combine(workingDirectory, FilePath));
 
-        public string GetConfigFilePath(string? workingDirectory) => Path.Combine(workingDirectory, FilePath);
+        public string GetConfigFilePath(string workingDirectory) => Path.Combine(workingDirectory, FilePath);
 
         public void Verify(string? workingDirectory, string? projectRootDirectory)
         {
@@ -40,7 +40,7 @@ public string SelectConfigFilePath(GitVersionOptions gitVersionOptions, IGitRepo
             return GetConfigFilePath(HasConfigFileAt(workingDirectory) ? workingDirectory : projectRootDirectory);
         }
 
-        public Config ReadConfig(string? workingDirectory)
+        public Config ReadConfig(string workingDirectory)
         {
             var configFilePath = GetConfigFilePath(workingDirectory);
 

src/GitVersion.Core/Configuration/ConfigProvider.cs

@@ -37,7 +37,7 @@ public Config Provide(Config? overrideConfig = null)
             return Provide(rootDirectory, overrideConfig);
         }
 
-        public Config Provide(string? workingDirectory, Config? overrideConfig = null) =>
+        public Config Provide(string workingDirectory, Config? overrideConfig = null) =>
             new ConfigurationBuilder()
                 .Add(this.configFileLocator.ReadConfig(workingDirectory))
                 .Add(overrideConfig ?? new Config())

src/GitVersion.Core/Git/IBranch.cs

@@ -2,7 +2,7 @@
 
 namespace GitVersion
 {
-    public interface IBranch : IEquatable<IBranch>, IComparable<IBranch>, INamedReference
+    public interface IBranch : IEquatable<IBranch?>, IComparable<IBranch>, INamedReference
     {
         ICommit? Tip { get; }
         bool IsRemote { get; }

src/GitVersion.Core/Git/ICommit.cs

@@ -3,7 +3,7 @@
 
 namespace GitVersion
 {
-    public interface ICommit : IEquatable<ICommit>, IComparable<ICommit>, IGitObject
+    public interface ICommit : IEquatable<ICommit?>, IComparable<ICommit>, IGitObject
     {
         IEnumerable<ICommit> Parents { get; }
         DateTimeOffset When { get; }

src/GitVersion.Core/Git/IGitObject.cs

@@ -2,7 +2,7 @@
 
 namespace GitVersion
 {
-    public interface IGitObject : IEquatable<IGitObject>, IComparable<IGitObject>
+    public interface IGitObject : IEquatable<IGitObject?>, IComparable<IGitObject>
     {
         IObjectId Id { get; }
         string Sha { get; }

src/GitVersion.Core/Git/IObjectId.cs

@@ -2,7 +2,7 @@
 
 namespace GitVersion
 {
-    public interface IObjectId : IEquatable<IObjectId>, IComparable<IObjectId>
+    public interface IObjectId : IEquatable<IObjectId?>, IComparable<IObjectId>
     {
         string Sha { get; }
         string ToString(int prefixLength);

src/GitVersion.Core/Git/IRefSpec.cs

@@ -2,7 +2,7 @@
 
 namespace GitVersion
 {
-    public interface IRefSpec : IEquatable<IRefSpec>, IComparable<IRefSpec>
+    public interface IRefSpec : IEquatable<IRefSpec?>, IComparable<IRefSpec>
     {
         string Specification { get; }
         RefSpecDirection Direction { get; }

src/GitVersion.Core/Git/IReference.cs

@@ -2,7 +2,7 @@
 
 namespace GitVersion
 {
-    public interface IReference : IEquatable<IReference>, IComparable<IReference>, INamedReference
+    public interface IReference : IEquatable<IReference?>, IComparable<IReference>, INamedReference
     {
         string TargetIdentifier { get; }
         IObjectId? ReferenceTargetId { get; }

src/GitVersion.Core/Git/IRemote.cs

@@ -3,7 +3,7 @@
 
 namespace GitVersion
 {
-    public interface IRemote : IEquatable<IRemote>, IComparable<IRemote>
+    public interface IRemote : IEquatable<IRemote?>, IComparable<IRemote>
     {
         string Name { get; }
         string Url { get; }

src/GitVersion.Core/Git/ITag.cs

@@ -2,7 +2,7 @@
 
 namespace GitVersion
 {
-    public interface ITag : IEquatable<ITag>, IComparable<ITag>, INamedReference
+    public interface ITag : IEquatable<ITag?>, IComparable<ITag>, INamedReference
     {
         string TargetSha { get; }
         ICommit? PeeledTargetCommit();

src/GitVersion.Core/Git/ReferenceName.cs

@@ -3,9 +3,9 @@
 
 namespace GitVersion
 {
-    public class ReferenceName : IEquatable<ReferenceName>, IComparable<ReferenceName>
+    public class ReferenceName : IEquatable<ReferenceName?>, IComparable<ReferenceName>
     {
-        private static readonly LambdaEqualityHelper<ReferenceName> equalityHelper = new(x => x?.Canonical);
+        private static readonly LambdaEqualityHelper<ReferenceName> equalityHelper = new(x => x.Canonical);
         private static readonly LambdaKeyComparer<ReferenceName, string> comparerHelper = new(x => x.Canonical);
 
         private const string LocalBranchPrefix = "refs/heads/";
@@ -46,7 +46,7 @@ public static ReferenceName Parse(string canonicalName)
         public bool IsTag { get; }
         public bool IsPullRequest { get; }
 
-        public bool Equals(ReferenceName other) => equalityHelper.Equals(this, other);
+        public bool Equals(ReferenceName? other) => equalityHelper.Equals(this, other);
         public int CompareTo(ReferenceName other) => comparerHelper.Compare(this, other);
         public override bool Equals(object obj) => Equals((obj as ReferenceName)!);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);

src/GitVersion.Core/Helpers/LambdaEqualityHelper.cs

@@ -7,9 +7,9 @@ namespace GitVersion.Helpers
     // see https://github.com/libgit2/libgit2sharp/blob/7af5c60f22f9bd6064204f84467cfa62bedd1147/LibGit2Sharp/Core/LambdaEqualityHelper.cs
     public class LambdaEqualityHelper<T>
     {
-        private readonly Func<T?, object?>[] equalityContributorAccessors;
+        private readonly Func<T, object?>[] equalityContributorAccessors;
 
-        public LambdaEqualityHelper(params Func<T?, object?>[] equalityContributorAccessors) =>
+        public LambdaEqualityHelper(params Func<T, object?>[] equalityContributorAccessors) =>
             this.equalityContributorAccessors = equalityContributorAccessors;
 
         public bool Equals(T? instance, T? other)

src/GitVersion.Core/Model/BranchCommit.cs

@@ -5,7 +5,7 @@ namespace GitVersion
     /// <summary>
     /// A commit, together with the branch to which the commit belongs.
     /// </summary>
-    public readonly struct BranchCommit
+    public readonly struct BranchCommit : IEquatable<BranchCommit?>
     {
         public static readonly BranchCommit Empty = new();
 
@@ -18,14 +18,9 @@ public BranchCommit(ICommit commit, IBranch branch) : this()
         public IBranch Branch { get; }
         public ICommit Commit { get; }
 
-        private bool Equals(BranchCommit other) => Equals(Branch, other.Branch) && Equals(Commit, other.Commit);
+        public bool Equals(BranchCommit? other) => Equals(Branch, other?.Branch) && Equals(Commit, other?.Commit);
 
-        public override bool Equals(object obj)
-        {
-            if (obj is null)
-                return false;
-            return obj is BranchCommit commit && Equals(commit);
-        }
+        public override bool Equals(object obj) => obj is null ? false : Equals(obj as BranchCommit?);
 
         public override int GetHashCode()
         {

src/GitVersion.Core/VersionCalculation/SemanticVersioning/SemanticVersion.cs

@@ -5,7 +5,7 @@
 
 namespace GitVersion
 {
-    public class SemanticVersion : IFormattable, IComparable<SemanticVersion>
+    public class SemanticVersion : IFormattable, IComparable<SemanticVersion>, IEquatable<SemanticVersion?>
     {
         private static readonly SemanticVersion Empty = new();
 

src/GitVersion.Core/VersionCalculation/SemanticVersioning/SemanticVersionBuildMetaData.cs

@@ -5,14 +5,14 @@
 
 namespace GitVersion
 {
-    public class SemanticVersionBuildMetaData : IFormattable, IEquatable<SemanticVersionBuildMetaData>
+    public class SemanticVersionBuildMetaData : IFormattable, IEquatable<SemanticVersionBuildMetaData?>
     {
         private static readonly Regex ParseRegex = new(
             @"(?<BuildNumber>\d+)?(\.?Branch(Name)?\.(?<BranchName>[^\.]+))?(\.?Sha?\.(?<Sha>[^\.]+))?(?<Other>.*)",
             RegexOptions.Compiled | RegexOptions.IgnoreCase);
 
         private static readonly LambdaEqualityHelper<SemanticVersionBuildMetaData> EqualityHelper =
-           new(x => x?.CommitsSinceTag, x => x?.Branch, x => x?.Sha);
+           new(x => x.CommitsSinceTag, x => x.Branch, x => x.Sha);
 
         public int? CommitsSinceTag;
         public string? Branch;

src/GitVersion.Core/VersionCalculation/SemanticVersioning/SemanticVersionPreReleaseTag.cs

@@ -7,10 +7,10 @@
 namespace GitVersion
 {
     public class SemanticVersionPreReleaseTag :
-        IFormattable, IComparable<SemanticVersionPreReleaseTag>, IEquatable<SemanticVersionPreReleaseTag>
+        IFormattable, IComparable<SemanticVersionPreReleaseTag>, IEquatable<SemanticVersionPreReleaseTag?>
     {
         private static readonly LambdaEqualityHelper<SemanticVersionPreReleaseTag> EqualityHelper =
-           new(x => x?.Name, x => x?.Number);
+           new(x => x.Name, x => x.Number);
 
         public SemanticVersionPreReleaseTag()
         {

src/GitVersion.LibGit2Sharp/Git/Branch.cs

@@ -5,7 +5,7 @@ namespace GitVersion
 {
     internal sealed class Branch : IBranch
     {
-        private static readonly LambdaEqualityHelper<IBranch> equalityHelper = new(x => x?.Name.Canonical);
+        private static readonly LambdaEqualityHelper<IBranch> equalityHelper = new(x => x.Name.Canonical);
         private static readonly LambdaKeyComparer<IBranch, string> comparerHelper = new(x => x.Name.Canonical);
 
         private readonly LibGit2Sharp.Branch innerBranch;
@@ -26,7 +26,7 @@ internal Branch(LibGit2Sharp.Branch branch)
         public ICommitCollection? Commits { get; }
 
         public int CompareTo(IBranch other) => comparerHelper.Compare(this, other);
-        public bool Equals(IBranch other) => equalityHelper.Equals(this, other);
+        public bool Equals(IBranch? other) => equalityHelper.Equals(this, other);
         public override bool Equals(object obj) => Equals((obj as IBranch)!);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);
         public override string ToString() => Name.ToString();

src/GitVersion.LibGit2Sharp/Git/Commit.cs

@@ -7,7 +7,7 @@ namespace GitVersion
 {
     internal sealed class Commit : GitObject, ICommit
     {
-        private static readonly LambdaEqualityHelper<ICommit> equalityHelper = new(x => x?.Id);
+        private static readonly LambdaEqualityHelper<ICommit> equalityHelper = new(x => x.Id);
         private static readonly LambdaKeyComparer<ICommit, string> comparerHelper = new(x => x.Sha);
 
         private readonly LibGit2Sharp.Commit innerCommit;
@@ -20,7 +20,7 @@ internal Commit(LibGit2Sharp.Commit innerCommit) : base(innerCommit)
         }
 
         public int CompareTo(ICommit other) => comparerHelper.Compare(this, other);
-        public bool Equals(ICommit other) => equalityHelper.Equals(this, other);
+        public bool Equals(ICommit? other) => equalityHelper.Equals(this, other);
         public override bool Equals(object obj) => Equals((obj as ICommit)!);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);
         public override string ToString() => $"{Id.ToString(7)} {this.innerCommit.MessageShort}";

src/GitVersion.LibGit2Sharp/Git/GitObject.cs

@@ -4,7 +4,7 @@ namespace GitVersion
 {
     internal class GitObject : IGitObject
     {
-        private static readonly LambdaEqualityHelper<IGitObject> equalityHelper = new(x => x?.Id);
+        private static readonly LambdaEqualityHelper<IGitObject> equalityHelper = new(x => x.Id);
         private static readonly LambdaKeyComparer<IGitObject, string> comparerHelper = new(x => x.Sha);
 
         internal GitObject(LibGit2Sharp.GitObject innerGitObject)
@@ -14,7 +14,7 @@ internal GitObject(LibGit2Sharp.GitObject innerGitObject)
         }
 
         public int CompareTo(IGitObject other) => comparerHelper.Compare(this, other);
-        public bool Equals(IGitObject other) => equalityHelper.Equals(this, other);
+        public bool Equals(IGitObject? other) => equalityHelper.Equals(this, other);
         public override bool Equals(object obj) => Equals((obj as IGitObject)!);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);
         public override string ToString() => Id.ToString(7);

src/GitVersion.LibGit2Sharp/Git/ObjectId.cs

@@ -4,7 +4,7 @@ namespace GitVersion
 {
     internal sealed class ObjectId : IObjectId
     {
-        private static readonly LambdaEqualityHelper<IObjectId> equalityHelper = new(x => x?.Sha);
+        private static readonly LambdaEqualityHelper<IObjectId> equalityHelper = new(x => x.Sha);
         private static readonly LambdaKeyComparer<IObjectId, string> comparerHelper = new(x => x.Sha);
 
         private readonly LibGit2Sharp.ObjectId innerObjectId;
@@ -15,7 +15,7 @@ public ObjectId(string sha) : this(new LibGit2Sharp.ObjectId(sha))
         }
 
         public int CompareTo(IObjectId other) => comparerHelper.Compare(this, other);
-        public bool Equals(IObjectId other) => equalityHelper.Equals(this, other);
+        public bool Equals(IObjectId? other) => equalityHelper.Equals(this, other);
         public override bool Equals(object obj) => Equals((obj as IObjectId)!);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);
         public override string ToString() => ToString(7);

src/GitVersion.LibGit2Sharp/Git/RefSpec.cs

@@ -4,14 +4,14 @@ namespace GitVersion
 {
     public class RefSpec : IRefSpec
     {
-        private static readonly LambdaEqualityHelper<IRefSpec> equalityHelper = new(x => x?.Specification);
+        private static readonly LambdaEqualityHelper<IRefSpec> equalityHelper = new(x => x.Specification);
         private static readonly LambdaKeyComparer<IRefSpec, string> comparerHelper = new(x => x.Specification);
 
         private readonly LibGit2Sharp.RefSpec innerRefSpec;
 
         internal RefSpec(LibGit2Sharp.RefSpec refSpec) => this.innerRefSpec = refSpec;
         public int CompareTo(IRefSpec other) => comparerHelper.Compare(this, other);
-        public bool Equals(IRefSpec other) => equalityHelper.Equals(this, other);
+        public bool Equals(IRefSpec? other) => equalityHelper.Equals(this, other);
         public override bool Equals(object obj) => Equals((obj as IRefSpec)!);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);
         public override string ToString() => Specification;

src/GitVersion.LibGit2Sharp/Git/Reference.cs

@@ -5,7 +5,7 @@ namespace GitVersion
 {
     internal sealed class Reference : IReference
     {
-        private static readonly LambdaEqualityHelper<IReference> equalityHelper = new(x => x?.Name.Canonical);
+        private static readonly LambdaEqualityHelper<IReference> equalityHelper = new(x => x.Name.Canonical);
         private static readonly LambdaKeyComparer<IReference, string> comparerHelper = new(x => x.Name.Canonical);
 
         internal readonly LibGit2Sharp.Reference innerReference;
@@ -22,7 +22,7 @@ internal Reference(LibGit2Sharp.Reference reference)
         public IObjectId? ReferenceTargetId { get; }
         public int CompareTo(IReference other) => comparerHelper.Compare(this, other);
         public override bool Equals(object obj) => Equals((obj as IReference)!);
-        public bool Equals(IReference other) => equalityHelper.Equals(this, other);
+        public bool Equals(IReference? other) => equalityHelper.Equals(this, other);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);
         public override string ToString() => Name.ToString();
         public string TargetIdentifier => this.innerReference.TargetIdentifier;

src/GitVersion.LibGit2Sharp/Git/Remote.cs

@@ -6,15 +6,15 @@ namespace GitVersion
 {
     internal sealed class Remote : IRemote
     {
-        private static readonly LambdaEqualityHelper<IRemote> equalityHelper = new(x => x?.Name);
+        private static readonly LambdaEqualityHelper<IRemote> equalityHelper = new(x => x.Name);
         private static readonly LambdaKeyComparer<IRemote, string> comparerHelper = new(x => x.Name);
 
         private readonly LibGit2Sharp.Remote innerRemote;
 
         internal Remote(LibGit2Sharp.Remote remote) => this.innerRemote = remote;
 
         public int CompareTo(IRemote other) => comparerHelper.Compare(this, other);
-        public bool Equals(IRemote other) => equalityHelper.Equals(this, other);
+        public bool Equals(IRemote? other) => equalityHelper.Equals(this, other);
         public override bool Equals(object obj) => Equals((obj as IRemote)!);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);
         public override string ToString() => Name;

src/GitVersion.LibGit2Sharp/Git/Tag.cs

@@ -5,7 +5,7 @@ namespace GitVersion
 {
     internal sealed class Tag : ITag
     {
-        private static readonly LambdaEqualityHelper<ITag> equalityHelper = new(x => x?.Name.Canonical);
+        private static readonly LambdaEqualityHelper<ITag> equalityHelper = new(x => x.Name.Canonical);
         private static readonly LambdaKeyComparer<ITag, string> comparerHelper = new(x => x.Name.Canonical);
 
         private readonly LibGit2Sharp.Tag innerTag;
@@ -17,7 +17,7 @@ internal Tag(LibGit2Sharp.Tag tag)
         public ReferenceName Name { get; }
 
         public int CompareTo(ITag other) => comparerHelper.Compare(this, other);
-        public bool Equals(ITag other) => equalityHelper.Equals(this, other);
+        public bool Equals(ITag? other) => equalityHelper.Equals(this, other);
         public override bool Equals(object obj) => Equals((obj as ITag)!);
         public override int GetHashCode() => equalityHelper.GetHashCode(this);
         public override string ToString() => Name.ToString();