feat(k8s): proper support for Helm charts

This brings Helm support close to parity with the container module
type. The vote-helm example project demonstrates its use.

This required some framework changes and additions, in order to
allow modules that contain manifests to reference sources from other
modules.

BREAKING CHANGES:

We now install Helm's Tiller service in each app namespace, instead
of cluster-wide, and we no longer prefix Helm release names.

docs/reference/commands.md

@@ -212,7 +212,7 @@ Examples:
     garden deploy service-a,service-b     # only deploy service-a and service-b
     garden deploy --force                 # force re-deploy of modules, even if they're already deployed
     garden deploy --watch                 # watch for changes to code
-    garden deploy --hot-reload=my-service # deploys all services, with hot reloading enabled for my-service
+    garden deploy --watch --hot-reload=my-service # deploys all services, with hot reloading enabled for my-service
     garden deploy --env stage             # deploy your services to an environment called stage
 
 ##### Usage

docs/reference/config.md

@@ -763,3 +763,370 @@ module:
         -
 ```
 
+### helm
+
+```yaml
+
+# Configure a module whose sources are located in this directory.
+#
+# Required.
+module: 
+  # The type of this module.
+  #
+  # Example: "container"
+  #
+  # Required.
+  type:
+
+  # The name of this module.
+  #
+  # Example: "my-sweet-module"
+  #
+  # Required.
+  name:
+
+  description:
+
+  # A remote repository URL. Currently only supports git servers. Must contain a hash suffix
+  # pointing to a specific branch or tag, with the format: <git remote url>#<branch|tag>
+  #
+  # Garden will import the repository source code into this module, but read the module's
+  # config from the local garden.yml file.
+  #
+  # Example: "git+https://github.com/org/repo.git#v2.0"
+  #
+  # Optional.
+  repositoryUrl:
+
+  # Variables that this module can reference and expose as environment variables.
+  #
+  # Example:
+  #   my-variable: some-value
+  #
+  # Optional.
+  variables: 
+    {}
+
+  # When false, disables pushing this module to remote registries.
+  #
+  # Optional.
+  allowPublish: true
+
+  # Specify how to build the module. Note that plugins may define additional keys on this object.
+  #
+  # Optional.
+  build: 
+    # The command to run inside the module's directory to perform the build.
+    #
+    # Example:
+    #   - npm
+    #   - run
+    #   - build
+    #
+    # Optional.
+    command: 
+      -
+
+    # A list of modules that must be built before this module is built.
+    #
+    # Example:
+    #   - name: some-other-module-name
+    #
+    # Optional.
+    dependencies: 
+      - # Module name to build ahead of this module.
+        #
+        # Required.
+        name:
+
+        # Specify one or more files or directories to copy from the built dependency to this
+        # module.
+        #
+        # Optional.
+        copy: 
+          - # POSIX-style path or filename of the directory or file(s) to copy to the target.
+            #
+            # Required.
+            source:
+
+            # POSIX-style path or filename to copy the directory or file(s) to (defaults to same
+            # as source path).
+            #
+            # Optional.
+            target:
+
+  # A valid Helm chart name or URI. Required if the module doesn't contain the Helm chart itself.
+  #
+  # Example: "stable/nginx-ingress"
+  #
+  # Optional.
+  chart:
+
+  # The path, relative to the module path, to the chart sources (i.e. where the Chart.yaml file
+  # is, if any).
+  #
+  # Optional.
+  chartPath: .
+
+  # List of names of services that should be deployed before this chart.
+  #
+  # Optional.
+  dependencies: 
+    # Valid RFC1035/RFC1123 (DNS) label (may contain lowercase letters, numbers and dashes, must
+    # start with a letter, and cannot end with a dash) and additionally cannot contain consecutive
+    # dashes, or be longer than 63 characters.
+    #
+    # Optional.
+    -
+
+  # The repository URL to fetch the chart from.
+  #
+  # Optional.
+  repo:
+
+  # The Deployment, DaemonSet or StatefulSet that Garden should regard as the _Garden service_ in
+  # this module (not to be confused with Kubernetes Service resources). Because a Helm chart can
+  # contain any number of Kubernetes resources, this needs to be specified for certain Garden
+  # features and commands to work, such as hot-reloading.
+  # We currently map a Helm chart to a single Garden service, because all the resources in a Helm
+  # chart are deployed at once.
+  #
+  # Optional.
+  serviceResource: 
+    # The type of Kubernetes resource to sync files to.
+    #
+    # Required.
+    # Allowed values: "Deployment", "DaemonSet", "StatefulSet"
+    kind: Deployment
+
+    # The name of the resource to sync to. If the chart contains a single resource of the
+    # specified Kind, this can be omitted.
+    # This can include a Helm template string, e.g. '{{ template "my-chart.fullname" . }}'. This
+    # allows you to easily match the dynamic names given by Helm. In most cases you should copy
+    # this directly from the template in question in order to match it. Note that you may need to
+    # add single quotes around the string for the YAML to be parsed correctly.
+    #
+    # Optional.
+    name:
+
+    # The name of a container in the target. Specify this if the target contains more than one
+    # container and the main container is not the first container in the spec.
+    #
+    # Optional.
+    containerName:
+
+    # The Garden module that contains the sources for the container. This needs to be specified
+    # under `serviceResource` in order to enable hot-reloading for the chart, but is not necessary
+    # for tasks and tests.
+    # Must be a `container` module, and for hot-reloading to work you must specify the `hotReload`
+    # field on the container module.
+    # Note: If you specify a module here, you don't need to specify it additionally under
+    # `build.dependencies`
+    #
+    # Example: "my-container-module"
+    #
+    # Optional.
+    containerModule:
+
+    # If specified, overrides the arguments for the main container when running in hot-reload
+    # mode.
+    #
+    # Example:
+    #   - nodemon
+    #   - my-server.js
+    #
+    # Optional.
+    hotReloadArgs: 
+      -
+
+  # The task definitions for this module.
+  #
+  # Optional.
+  tasks: 
+    # Required configuration for module tests.
+    #
+    # Optional.
+    - # The name of the test.
+      #
+      # Required.
+      name:
+
+      # The names of any services that must be running, and the names of any tasks that must be
+      # executed, before the test is run.
+      #
+      # Optional.
+      dependencies: 
+        -
+
+      # Maximum duration (in seconds) of the test run.
+      #
+      # Optional.
+      timeout: null
+
+      # The Deployment, DaemonSet or StatefulSet that Garden should use to execute this task. If
+      # not specified, the `serviceResource` configured on the module will be used. If neither is
+      # specified, an error will be thrown.
+      #
+      # Optional.
+      resource: 
+        # The type of Kubernetes resource to sync files to.
+        #
+        # Required.
+        # Allowed values: "Deployment", "DaemonSet", "StatefulSet"
+        kind: Deployment
+
+        # The name of the resource to sync to. If the chart contains a single resource of the
+        # specified Kind, this can be omitted.
+        # This can include a Helm template string, e.g. '{{ template "my-chart.fullname" . }}'.
+        # This allows you to easily match the dynamic names given by Helm. In most cases you
+        # should copy this directly from the template in question in order to match it. Note that
+        # you may need to add single quotes around the string for the YAML to be parsed correctly.
+        #
+        # Optional.
+        name:
+
+        # The name of a container in the target. Specify this if the target contains more than one
+        # container and the main container is not the first container in the spec.
+        #
+        # Optional.
+        containerName:
+
+        # The Garden module that contains the sources for the container. This needs to be
+        # specified under `serviceResource` in order to enable hot-reloading for the chart, but is
+        # not necessary for tasks and tests.
+        # Must be a `container` module, and for hot-reloading to work you must specify the
+        # `hotReload` field on the container module.
+        # Note: If you specify a module here, you don't need to specify it additionally under
+        # `build.dependencies`
+        #
+        # Example: "my-container-module"
+        #
+        # Optional.
+        containerModule:
+
+        # If specified, overrides the arguments for the main container when running in hot-reload
+        # mode.
+        #
+        # Example:
+        #   - nodemon
+        #   - my-server.js
+        #
+        # Optional.
+        hotReloadArgs: 
+          -
+
+      # The arguments to pass to the pod used for execution.
+      #
+      # Optional.
+      args: 
+        -
+
+      # Key/value map of environment variables. Keys must be valid POSIX environment variable
+      # names (must not start with `GARDEN`) and values must be primitives.
+      #
+      # Optional.
+      env: 
+        {}
+
+  # The test suite definitions for this module.
+  #
+  # Optional.
+  tests: 
+    # Required configuration for module tests.
+    #
+    # Optional.
+    - # The name of the test.
+      #
+      # Required.
+      name:
+
+      # The names of any services that must be running, and the names of any tasks that must be
+      # executed, before the test is run.
+      #
+      # Optional.
+      dependencies: 
+        -
+
+      # Maximum duration (in seconds) of the test run.
+      #
+      # Optional.
+      timeout: null
+
+      # The Deployment, DaemonSet or StatefulSet that Garden should use to execute this test
+      # suite. If not specified, the `serviceResource` configured on the module will be used. If
+      # neither is specified, an error will be thrown.
+      #
+      # Optional.
+      resource: 
+        # The type of Kubernetes resource to sync files to.
+        #
+        # Required.
+        # Allowed values: "Deployment", "DaemonSet", "StatefulSet"
+        kind: Deployment
+
+        # The name of the resource to sync to. If the chart contains a single resource of the
+        # specified Kind, this can be omitted.
+        # This can include a Helm template string, e.g. '{{ template "my-chart.fullname" . }}'.
+        # This allows you to easily match the dynamic names given by Helm. In most cases you
+        # should copy this directly from the template in question in order to match it. Note that
+        # you may need to add single quotes around the string for the YAML to be parsed correctly.
+        #
+        # Optional.
+        name:
+
+        # The name of a container in the target. Specify this if the target contains more than one
+        # container and the main container is not the first container in the spec.
+        #
+        # Optional.
+        containerName:
+
+        # The Garden module that contains the sources for the container. This needs to be
+        # specified under `serviceResource` in order to enable hot-reloading for the chart, but is
+        # not necessary for tasks and tests.
+        # Must be a `container` module, and for hot-reloading to work you must specify the
+        # `hotReload` field on the container module.
+        # Note: If you specify a module here, you don't need to specify it additionally under
+        # `build.dependencies`
+        #
+        # Example: "my-container-module"
+        #
+        # Optional.
+        containerModule:
+
+        # If specified, overrides the arguments for the main container when running in hot-reload
+        # mode.
+        #
+        # Example:
+        #   - nodemon
+        #   - my-server.js
+        #
+        # Optional.
+        hotReloadArgs: 
+          -
+
+      # The arguments to pass to the pod used for testing.
+      #
+      # Optional.
+      args: 
+        -
+
+      # Key/value map of environment variables. Keys must be valid POSIX environment variable
+      # names (must not start with `GARDEN`) and values must be primitives.
+      #
+      # Optional.
+      env: 
+        {}
+
+  # The chart version to deploy.
+  #
+  # Optional.
+  version:
+
+  # Map of values to pass to Helm when rendering the templates. May include arrays and nested
+  # objects.
+  #
+  # Optional.
+  values: 
+    {}
+```
+

docs/using-garden/README.md

@@ -14,4 +14,8 @@ Most of the time we want to develop locally, with our project running in Minikub
 
 ## [Hot Reload](./hot-reload.md)
 
-This article discusses how to use hot reloading, so that you can update running services on the fly as you make changes to their code, without losing state and without having to destroy and re-create your container.
+This article discusses how to use hot reloading, so that you can update running services on the fly as you make changes to their code, without losing state and without having to destroy and re-create your container.
+
+## [Using Helm charts](./using-helm-charts.md)
+
+The [Helm](https://helm.sh/) package manager is one of the most commonly used tools for managing Kubernetes manifests. Garden supports using your own Helm charts, alongside your container modules. This guide shows you how to use 3rd-party (or otherwise external) Helm charts, as well as your own charts in your Garden project. We also go through how to configure tests, tasks and hot-reloading for your charts.