add backwards compatibility and default argument for incremental_predicates (#6628) (#6660)

* add backwards compatibility and default argument

* changie <3

* Update .changes/unreleased/Fixes-20230117-101342.yaml

Co-authored-by: Jeremy Cohen <jeremy@dbtlabs.com>
(cherry picked from commit f841a7c)

Co-authored-by: dave-connors-3 <73915542+dave-connors-3@users.noreply.github.com>

Author: github-actions[bot]

.changes/unreleased/Fixes-20230117-101342.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Provide backward compatibility for `get_merge_sql` arguments
+time: 2023-01-17T10:13:42.118336-06:00
+custom:
+  Author: dave-connors-3
+  Issue: "6625"

core/dbt/include/global_project/macros/materializations/models/incremental/merge.sql

@@ -1,8 +1,10 @@
-{% macro get_merge_sql(target, source, unique_key, dest_columns, incremental_predicates) -%}
+{% macro get_merge_sql(target, source, unique_key, dest_columns, incremental_predicates=none) -%}
+   -- back compat for old kwarg name
+  {% set incremental_predicates = kwargs.get('predicates', incremental_predicates) %}
   {{ adapter.dispatch('get_merge_sql', 'dbt')(target, source, unique_key, dest_columns, incremental_predicates) }}
 {%- endmacro %}
 
-{% macro default__get_merge_sql(target, source, unique_key, dest_columns, incremental_predicates) -%}
+{% macro default__get_merge_sql(target, source, unique_key, dest_columns, incremental_predicates=none) -%}
     {%- set predicates = [] if incremental_predicates is none else [] + incremental_predicates -%}
     {%- set dest_cols_csv = get_quoted_csv(dest_columns | map(attribute="name")) -%}
     {%- set merge_update_columns = config.get('merge_update_columns') -%}