Add instructions for migrations work-around

Creating initial migrations that don't create new SQL tables seems to
fail silently for some reason. This commit adds some information about a
work-around to the README and example files.

README.md

@@ -124,8 +124,13 @@ format:
     VERSION_migration_name.up.sql
     VERSION_migration_name.down.sql
 
+The first migration file must generate a table (as opposed to an SQL function,
+for example) with at least one field. Without this, the migration command will
+fail silently. If you would like to create an SQL function in your first
+migration an example work-around can be found
+[here](https://github.com/kohrVid/pg-cli/blob/master/example/migrations/1_initialise_schema.up.sql).
 Further details on how to write migration files can be found
-[here](https://github.com/golang-migrate/migrate/blob/master/MIGRATIONS.md).
+on the [golang-migrate github repo](https://github.com/golang-migrate/migrate/blob/master/MIGRATIONS.md).
 
 Apply all up migrations:
 

db/migrations_test.go

@@ -43,7 +43,7 @@ func TestMigrateUp(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	checkDBVersion(t, conf, "../example/migrations", 1)
+	checkDBVersion(t, conf, "../example/migrations", 2)
 
 	forceDBDrop(conf)
 }

example/migrations/1_initialise_schema.down.sql

@@ -0,0 +1,2 @@
+DROP FUNCTION modify_updated_at_column();
+DROP TABLE table0;

example/migrations/1_initialise_schema.up.sql

@@ -0,0 +1,13 @@
+CREATE TABLE IF NOT EXISTS table0 (
+  field VARCHAR(16)
+);
+
+CREATE OR REPLACE FUNCTION modify_updated_at_column()
+  RETURNS TRIGGER AS $$
+  BEGIN
+    NEW.updated_at = now();
+    RETURN NEW;
+  END;
+$$ language 'plpgsql';
+
+DROP TABLE table0;