Add rigm to upgrade guide (#2667)

Update docs to be accurate for 3.0

third_party/terraform/website/docs/guides/version_3_upgrade.html.markdown

@@ -77,13 +77,14 @@ so Terraform knows to manage them.
 - [Resource: `google_compute_health_check`](#resource-google_compute_health_check)
 - [Resource: `google_compute_image`](#resource-google_compute_image)
 - [Resource: `google_compute_instance`](#resource-google_compute_instance)
+- [Resource: `google_compute_instance_group_manager`](#resource-google_compute_instance_group_manager)
 - [Resource: `google_compute_instance_template`](#resource-google_compute_instance_template)
 - [Resource: `google_compute_network`](#resource-google_compute_network)
 - [Resource: `google_compute_network_peering`](#resource-google_compute_network_peering)
 - [Resource: `google_compute_node_template`](#resource-google_compute_node_template)
 - [Resource: `google_compute_region_backend_service`](#resource-google_compute_region_backend_service)
 - [Resource: `google_compute_region_health_check`](#resource-google_compute_region_health_check)
-- [Resource: `google_compute_region_instance_group_manager`](#resource-google_compute_region_instance_group_manager)
+- [Resource: `google_compute_region_instance_group_manager`](#resource-google_compute_instance_group_manager)
 - [Resource: `google_compute_resource_policy`](#resource-google_compute_resource_policy)
 - [Resource: `google_compute_route`](#resource-google_compute_route)
 - [Resource: `google_compute_router`](#resource-google_compute_router)
@@ -583,6 +584,52 @@ or `enable_integrity_monitoring` is now required on the `shielded_instance_confi
 In an attempt to avoid allowing empty blocks in config files, at least one of `on_host_maintenance`, `automatic_restart`,
 `preemptible`, or `node_affinities` is now required on the `scheduling` block.
 
+## Resource: `google_compute_instance_group_manager`
+
+The following changes apply to both `google_compute_instance_group_manager` and `google_compute_region_instance_group_manager`.
+
+### `instance_template` has been replaced by `version.instance_template`
+
+Instance group managers should be using `version` blocks to reference which
+instance template to use for provisioning. To upgrade use a single `version`
+block with `instance_template` in your config and by default all traffic will be
+directed to that version.
+
+### Old Config
+
+```hcl
+resource "google_compute_instance_group_manager" "my_igm" {
+    name               = "my-igm"
+    zone               = "us-central1-c"
+    base_instance_name = "igm"
+
+    instance_template = "${google_compute_instance_template.my_tmpl.self_link}"
+}
+```
+
+### New Config
+
+```hcl
+resource "google_compute_instance_group_manager" "my_igm" {
+    name               = "my-igm"
+    zone               = "us-central1-c"
+    base_instance_name = "igm"
+
+    version {
+        name = "prod"
+        instance_template = "${google_compute_instance_template.my_tmpl.self_link}"
+    }
+}
+```
+
+### `update_strategy` has been replaced by `update_policy`
+
+To allow much greater control over the updates happening to instance groups
+`update_strategy` has been replaced by `update_policy`. The previous
+functionality to determine if instance should be replaced or restarted can be
+achieved using `update_policy.minimal_action`. For more details see the
+[official guide](https://cloud.google.com/compute/docs/instance-groups/rolling-out-updates-to-managed-instance-groups).
+
 ## Resource: `google_compute_instance_template`
 
 ### At least one of `enable_secure_boot`, `enable_vtpm`, or `enable_integrity_monitoring` is now required on `google_compute_instance_template.shielded_instance_config`
@@ -723,13 +770,6 @@ In an attempt to avoid allowing empty blocks in config files, at least one of `h
 In an attempt to avoid allowing empty blocks in config files, at least one of `request`, `response`, `port`, `port_name`,
 `proxy_header`, or `port_specification` is now required on the `ssl_health_check` and `tcp_health_check` blocks.
 
-## Resource: `google_compute_region_instance_group_manager`
-
-### `update_strategy` no longer has any effect and is removed
-
-With `rolling_update_policy` removed, `update_strategy` has no effect anymore.
-Before updating, remove it from your config.
-
 ## Resource: `google_compute_resource_policy`
 
 ### Exactly one of `hourly_schedule`, `daily_schedule` or `weekly_schedule` on `google_compute_resource_policy.snapshot_schedule_policy.schedule`

third_party/terraform/website/docs/r/compute_instance_group_manager.html.markdown

@@ -94,16 +94,9 @@ The following arguments are supported:
     appending a hyphen and a random four-character string to the base instance
     name.
 
-* `instance_template` - (Deprecated) The
-  full URL to an instance template from which all new instances
-  will be created. This field is replaced by `version.instance_template`. You must
-  specify at least one `version` block with an `instance_template`.
-
-* `version` - (Optional) Application versions managed by this instance group. Each
+* `version` - (Required) Application versions managed by this instance group. Each
     version deals with a specific instance template, allowing canary release scenarios.
     Structure is documented below.
-    Until `instance_template` is removed this field will be Optional to allow for a
-    graceful upgrade. In the Beta provider and as of 3.0.0 it will be Required.
 
 * `name` - (Required) The name of the instance group manager. Must be 1-63
     characters long and comply with
@@ -124,9 +117,6 @@ The following arguments are supported:
 * `project` - (Optional) The ID of the project in which the resource belongs. If it
     is not provided, the provider project is used.
 
-* `update_strategy` - (Deprecated)  This field has been deprecated, use `update_policy`
-  instead.
-
 * `target_size` - (Optional) The target number of running instances for this managed
     instance group. This value should always be explicitly set unless this resource is attached to
      an autoscaler, in which case it should never be set. Defaults to `0`.

third_party/terraform/website/docs/r/compute_region_instance_group_manager.html.markdown

@@ -92,16 +92,9 @@ The following arguments are supported:
     appending a hyphen and a random four-character string to the base instance
     name.
 
-* `instance_template` - (Deprecated) The
-  full URL to an instance template from which all new instances
-  will be created. This field is replaced by `version.instance_template`. You must
-  specify at least one `version` block with an `instance_template`.
-
-* `version` - (Optional) Application versions managed by this instance group. Each
+* `version` - (Required) Application versions managed by this instance group. Each
     version deals with a specific instance template, allowing canary release scenarios.
     Structure is documented below.
-    Until `instance_template` is removed this field will be Optional to allow for a
-    graceful upgrade. In the Beta provider and as of 3.0.0 it will be Required.
 
 * `name` - (Required) The name of the instance group manager. Must be 1-63
     characters long and comply with