Reverse the order of INSERT statements in structure.sql dumps

This was suggested as a better fix in #43414. The goal is to decrease merge conflicts that often come at the bottom due to the semi colon placement.

We've been running with a monkey patch for it for about a month, and can confirm, it's definitely an improvement. So I'm making this as an alternative suggestion to #43414

Adding @mlarraz as a co-author - thanks for the original inspiration.

Co-authored-by: @mlarraz <mlarraz@users.noreply.github.com>

activerecord/CHANGELOG.md

@@ -1,3 +1,13 @@
+*   Reversed the order of `INSERT` statements in `structure.sql` dumps
+
+    This should decrease the likelihood of merge conflicts. New migrations
+    will now be added at the top of the list.
+
+    For existing apps, there will be a large diff the next time `structure.sql`
+    is generated.
+
+    *Alex Ghiculescu*, *Matt Larraz*
+
 *   Fix PG.connect keyword arguments deprecation warning on ruby 2.7
 
     Fixes #44307.

activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

@@ -1675,7 +1675,7 @@ def insert_versions_sql(versions)
 
           if versions.is_a?(Array)
             sql = +"INSERT INTO #{sm_table} (version) VALUES\n"
-            sql << versions.map { |v| "(#{quote(v)})" }.join(",\n")
+            sql << versions.reverse.map { |v| "(#{quote(v)})" }.join(",\n")
             sql << ";\n\n"
             sql
           else

activerecord/test/cases/schema_dumper_test.rb

@@ -25,15 +25,21 @@ def test_dump_schema_information_with_empty_versions
     assert_no_match(/INSERT INTO/, schema_info)
   end
 
-  def test_dump_schema_information_outputs_lexically_ordered_versions
+  def test_dump_schema_information_outputs_lexically_reverse_ordered_versions_regardless_of_database_order
     versions = %w{ 20100101010101 20100201010101 20100301010101 }
-    versions.reverse_each do |v|
+    versions.shuffle.each do |v|
       ActiveRecord::SchemaMigration.create!(version: v)
     end
 
     schema_info = ActiveRecord::Base.connection.dump_schema_information
-    assert_match(/20100201010101.*20100301010101/m, schema_info)
-    assert_includes schema_info, "20100101010101"
+    expected = <<~STR
+    INSERT INTO #{ActiveRecord::Base.connection.quote_table_name("schema_migrations")} (version) VALUES
+    ('20100301010101'),
+    ('20100201010101'),
+    ('20100101010101');
+
+    STR
+    assert_equal expected, schema_info
   ensure
     ActiveRecord::SchemaMigration.delete_all
   end