Merge branch 'docs-praefect-strong-consistency-on-13.6' into 'master'

Update how to enable strong consistency and feature version history

See merge request gitlab-org/gitlab!58482

doc/administration/gitaly/praefect.md

@@ -945,8 +945,10 @@ 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.
+> - In GitLab 13.3, disabled unless primary-wins voting strategy is disabled.
 > - From GitLab 13.4, enabled by default.
+> - From GitLab 13.5, you must use Git v2.28.0 or higher on Gitaly nodes to enable strong consistency.
+> - From GitLab 13.6, primary-wins voting strategy and `gitaly_reference_transactions_primary_wins` feature flag were removed from the source code.
 
 Praefect guarantees eventual consistency by replicating all writes to secondary nodes
 after the write to the primary Gitaly node has happened.
@@ -958,18 +960,12 @@ information, see the [strong consistency epic](https://gitlab.com/groups/gitlab-
 
 To enable strong consistency:
 
-- In GitLab 13.5, you must use Git v2.28.0 or higher on Gitaly nodes to enable
-  strong consistency.
-- In GitLab 13.4 and later, the strong consistency voting strategy has been
-  improved. Instead of requiring all nodes to agree, only the primary and half
-  of the secondaries need to agree. This strategy is enabled by default. To
-  disable it and continue using the primary-wins strategy, enable the
-  `:gitaly_reference_transactions_primary_wins` feature flag.
-- In GitLab 13.3, 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 13.5, you must use Git v2.28.0 or higher on Gitaly nodes to enable strong consistency.
+- In GitLab 13.4 and later, the strong consistency voting strategy has been improved and enabled by default.
+  Instead of requiring all nodes to agree, only the primary and half of the secondaries need to agree.
+- In GitLab 13.3, 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.
@@ -982,6 +978,9 @@ Feature.enable(:gitaly_reference_transactions)
 Feature.disable(:gitaly_reference_transactions_primary_wins)
 ```
 
+NOTE:
+If not set in GitLab, flags are read as false from the console and Praefect uses their default value, which depends on the GitLab version.
+
 To monitor strong consistency, you can use the following Prometheus metrics:
 
 - `gitaly_praefect_transactions_total`: Number of transactions created and