Add Cake dotnet tool directive instructions (#8440)

Addresses #8381
Relates to #8434

Author: augustoproiete

src/NuGetGallery/Extensions/CakeBuildManagerExtensions.cs

@@ -15,13 +15,19 @@ public static bool IsCakeExtension(this DisplayPackageViewModel model)
 
         public static string GetCakeInstallPackageCommand(this DisplayPackageViewModel model)
         {
-            var reference = $"nuget:?package={model.Id}&version={model.Version}";
+            var scheme = model.IsDotnetToolPackageType ? "dotnet" : "nuget";
+            var reference = $"{scheme}:?package={model.Id}&version={model.Version}";
 
             if (model.Prerelease)
             {
                 reference += "&prerelease";
             }
 
+            if (model.IsDotnetToolPackageType)
+            {
+                return $"#tool {reference}";
+            }
+
             if (IsCakeAddin(model))
             {
                 return $"#addin {reference}";

src/NuGetGallery/Views/Packages/DisplayPackage.cshtml

@@ -36,6 +36,12 @@
                 AlertLevel = AlertLevel.Info,
                 AlertMessage = "This package contains a <a href='https://aka.ms/global-tools'>.NET Core Global Tool</a> you can call from the shell/command line.",
             },
+
+            new ThirdPartyPackageManagerViewModel("Cake", "https://cakebuild.net/support/nuget")
+            {
+                Id = "cake-dotnet-tool",
+                InstallPackageCommand = Model.GetCakeInstallPackageCommand(),
+            },
         };
     }
     else if (Model.IsDotnetNewTemplatePackageType)

tests/NuGetGallery.Facts/Extensions/CakeBuildManagerExtensionsFacts.cs

@@ -48,6 +48,40 @@ public void ReturnsFalse(string[] tags)
 
         public class TheMethodGetCakeInstallPackageCommand
         {
+            public class GivenADotnetToolPackage
+            {
+                [Fact]
+                public void ReturnsADotNetToolDirective()
+                {
+                    var model = new DisplayPackageViewModel
+                    {
+                        IsDotnetToolPackageType = true,
+                        Id = "dotnet-reportgenerator-globaltool",
+                        Version = "1.0.0",
+                    };
+
+                    var actual = model.GetCakeInstallPackageCommand();
+
+                    Assert.Equal("#tool dotnet:?package=dotnet-reportgenerator-globaltool&version=1.0.0", actual);
+                }
+
+                [Fact]
+                public void ReturnsADotNetToolDirectiveWithPrerelease()
+                {
+                    var model = new DisplayPackageViewModel
+                    {
+                        IsDotnetToolPackageType = true,
+                        Id = "dotnet-reportgenerator-globaltool",
+                        Version = "1.0.0-preview",
+                        Prerelease = true,
+                    };
+
+                    var actual = model.GetCakeInstallPackageCommand();
+
+                    Assert.Equal("#tool dotnet:?package=dotnet-reportgenerator-globaltool&version=1.0.0-preview&prerelease", actual);
+                }
+            }
+
             public class GivenAPackageWithTheCakeAddinTag
             {
                 [Fact]