Merge branch 'pks-gitaly-strong-consistency-flags' into 'master'

Update documentatiton on how to enable strong consistency

See merge request gitlab-org/gitlab!39193

doc/administration/gitaly/praefect.md

@@ -979,6 +979,7 @@ They reflect configuration defined for this instance of Praefect.
 
 > - Introduced in GitLab 13.1 in [alpha](https://about.gitlab.com/handbook/product/gitlab-the-product/#alpha-beta-ga), disabled by default.
 > - Entered [beta](https://about.gitlab.com/handbook/product/gitlab-the-product/#alpha-beta-ga) in GitLab 13.2, disabled by default.
+> - From GitLab 13.3, disabled unless primary-wins reference transactions strategy is disabled.
 
 Praefect guarantees eventual consistency by replicating all writes to secondary nodes
 after the write to the primary Gitaly node has happened.
@@ -991,15 +992,21 @@ information, see the [strong consistency epic](https://gitlab.com/groups/gitlab-
 
 To enable strong consistency:
 
-- In GitLab 13.2 and later, enable the `:gitaly_reference_transactions` feature flag.
+- In GitLab 13.3 and later, reference transactions are enabled by default with
+  a primary-wins strategy. This strategy causes all transactions to succeed for
+  the primary and thus does not ensure strong consistency. To enable strong
+  consistency, disable the `:gitaly_reference_transactions_primary_wins`
+  feature flag.
+- In GitLab 13.2, enable the `:gitaly_reference_transactions` feature flag.
 - In GitLab 13.1, enable the `:gitaly_reference_transactions` and `:gitaly_hooks_rpc`
   feature flags.
 
-Enabling feature flags requires [access to the Rails console](../feature_flags.md#start-the-gitlab-rails-console).
+Changing feature flags requires [access to the Rails console](../feature_flags.md#start-the-gitlab-rails-console).
 In the Rails console, enable or disable the flags as required. For example:
 
 ```ruby
 Feature.enable(:gitaly_reference_transactions)
+Feature.disable(:gitaly_reference_transactions_primary_wins)
 ```
 
 To monitor strong consistency, use the `gitaly_praefect_transactions_total` and