renamed destroy_all to truncate. (#134)

* renamed destroy_all to truncate. fixes #110

* make truncate a class method since it's not chainable like other instance methods

spec/query_spec.cr

@@ -563,4 +563,13 @@ describe Avram::Query do
       end
     end
   end
+
+  describe "truncate" do
+    it "truncates the table" do
+      10.times { UserBox.create }
+      UserQuery.new.select_count.should eq 10
+      UserQuery.truncate
+      UserQuery.new.select_count.should eq 0
+    end
+  end
 end

src/avram/query.cr

@@ -1,7 +1,8 @@
 require "./queryable"
 
 abstract class Avram::Query
-  def destroy_all
+  # runs a SQL `TRUNCATE` on the current table
+  def self.truncate
     Avram::Repo.run do |db|
       db.exec "TRUNCATE TABLE #{@@table_name}"
     end

src/avram/repo.cr

@@ -22,6 +22,7 @@ class Avram::Repo
     transactions[Fiber.current.object_id]?
   end
 
+  # runs a SQL `TRUNCATE` on all tables in the database
   def self.truncate
     DatabaseCleaner.new.truncate
   end