(GH-1932) Add missing wyam.cake file

The wyam.cake file was not included in the original commit, as it was
being ignored in the .gitignore file.

Author: gep13

.gitignore

@@ -85,7 +85,7 @@ _NCrunch_GitVersion
 GitVersion.sln.ide/
 .vs/
 Packages/
-build/
+build/*
 site/
 /TestResult.xml
 

build/wyam.cake

@@ -0,0 +1,31 @@
+Task("Clean-Documentation")
+    .Does(() =>
+{
+    EnsureDirectoryExists(MakeAbsolute(Directory("artifacts/temp/_PublishedDocumentation")));
+});
+
+Task("Preview-Documentation")
+    .WithCriteria(() => DirectoryExists(MakeAbsolute(Directory("docs"))), "Wyam documentation directory is missing")
+    .Does<BuildParameters>((parameters) =>
+{
+    Wyam(new WyamSettings
+    {
+        Recipe = "Docs",
+        Theme = "Samson",
+        OutputPath = MakeAbsolute(MakeAbsolute(Directory("artifacts/Documentation"))),
+        RootPath = MakeAbsolute(Directory("docs")),
+        Preview = true,
+        Watch = true,
+        ConfigurationFile = MakeAbsolute((FilePath)"config.wyam"),
+        PreviewVirtualDirectory = "GitVersion",
+        Settings = new Dictionary<string, object>
+        {
+            { "Host",  "gittools.github.io" },
+            { "LinkRoot",  "GitVersion" },
+            { "BaseEditUrl", "https://github.com/gittools/GitVersion/tree/master/docs/input/" },
+            { "SourceFiles", parameters.Paths.Directories.Source + "/**/{!bin,!obj,!packages,!*.Tests,}/**/*.cs" },
+            { "Title", "GitVersion" },
+            { "IncludeGlobalNamespace", false }
+        }
+    });
+});