truncate config table on migrate to db task

CHANGELOG.md

@@ -26,6 +26,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Store status data inside Flag activity
 - Deprecated (reorganized as `UserRelationship` entity) User fields with user AP IDs (`blocks`, `mutes`, `muted_reblogs`, `muted_notifications`, `subscribers`).
 - Logger: default log level changed from `warn` to `info`.
+- Config mix task `migrate_to_db` truncates `config` table before migrating the config file.
 <details>
   <summary>API Changes</summary>
 

lib/mix/tasks/pleroma/config.ex

@@ -52,6 +52,8 @@ def migrate_to_db(file_path \\ nil) do
 
   defp do_migrate_to_db(config_file) do
     if File.exists?(config_file) do
+      Ecto.Adapters.SQL.query!(Repo, "TRUNCATE config;")
+
       custom_config =
         config_file
         |> read_file()

test/tasks/config_test.exs

@@ -34,9 +34,13 @@ test "error if file with custom settings doesn't exist" do
                    15
   end
 
-  test "settings are migrated to db" do
+  describe "migrate_to_db/1" do
+    setup do
       initial = Application.get_env(:quack, :level)
       on_exit(fn -> Application.put_env(:quack, :level, initial) end)
+    end
+
+    test "settings are migrated to db" do
       assert Repo.all(ConfigDB) == []
 
       Mix.Tasks.Pleroma.Config.migrate_to_db("test/fixtures/config/temp.secret.exs")
@@ -51,6 +55,22 @@ test "settings are migrated to db" do
       assert ConfigDB.from_binary(config3.value) == :info
     end
 
+    test "config table is truncated before migration" do
+      ConfigDB.create(%{
+        group: ":pleroma",
+        key: ":first_setting",
+        value: [key: "value", key2: ["Activity"]]
+      })
+
+      assert Repo.aggregate(ConfigDB, :count, :id) == 1
+
+      Mix.Tasks.Pleroma.Config.migrate_to_db("test/fixtures/config/temp.secret.exs")
+
+      config = ConfigDB.get_by_params(%{group: ":pleroma", key: ":first_setting"})
+      assert ConfigDB.from_binary(config.value) == [key: "value", key2: [Repo]]
+    end
+  end
+
   describe "with deletion temp file" do
     setup do
       temp_file = "config/temp.exported_from_db.secret.exs"