(#174) Don't always push latest tag to docker

Update Docker build to only set latest tag when it is the latest build.
Previously we would set the latest tag on every tagged build which means
that pre-release and support builds would get tagged as latest. This
corrects that.

Chocolatey.Cake.Recipe/Content/docker.cake

@@ -66,7 +66,7 @@ BuildParameters.Tasks.DockerPush = Task("DockerPush")
 });
 
 BuildParameters.Tasks.DockerTagAsLatest = Task("DockerTagAsLatest")
-    .WithCriteria(() => BuildParameters.IsTagged && BuildParameters.Version.MajorMinorPatch == BuildParameters.Version.FullSemVersion, "Skipping because this isn't a tagged full release build.")
+    .WithCriteria(() => BuildParameters.BranchType == BranchType.Master && BuildParameters.IsTagged && BuildParameters.Version.MajorMinorPatch == BuildParameters.Version.FullSemVersion, "Skipping because this isn't a tagged full release build.")
     .WithCriteria(() => BuildParameters.DockerCredentials.HasCredentials, "Skipping because Docker Credentials were not provided.")
     .WithCriteria(() => BuildParameters.ShouldRunDocker, "Skipping because running Docker tasks is not enabled")
     .IsDependentOn("DockerLogin")
@@ -116,14 +116,16 @@ BuildParameters.Tasks.DockerManifest = Task("DockerManifest")
 
     DockerManifestPush(manifestListName);
 
-    // Create the latest manifest
-    DockerManifestCreate(
-        string.Format("{0}/{1}:latest", BuildParameters.RepositoryOwner, BuildParameters.RepositoryName),
-        string.Format("{0}/{1}:latest-windows", BuildParameters.RepositoryOwner, BuildParameters.RepositoryName),
-        new string[] {
-            string.Format("{0}/{1}:latest-linux", BuildParameters.RepositoryOwner, BuildParameters.RepositoryName)
-        }
-    );
-
-    DockerManifestPush(string.Format("{0}/{1}:latest", BuildParameters.RepositoryOwner, BuildParameters.RepositoryName));
+    // Create the latest manifest only if this is the master branch.
+    if (BuildParameters.BranchType == BranchType.Master) {
+        DockerManifestCreate(
+            string.Format("{0}/{1}:latest", BuildParameters.RepositoryOwner, BuildParameters.RepositoryName),
+            string.Format("{0}/{1}:latest-windows", BuildParameters.RepositoryOwner, BuildParameters.RepositoryName),
+            new string[] {
+                string.Format("{0}/{1}:latest-linux", BuildParameters.RepositoryOwner, BuildParameters.RepositoryName)
+            }
+        );
+
+        DockerManifestPush(string.Format("{0}/{1}:latest", BuildParameters.RepositoryOwner, BuildParameters.RepositoryName));
+    }
 });