Git is a distributed version control system.
Git is free software under the GPL.
Git has a mutable index called stage. 
Git tracks changes of files.
add something new to git push origin master
Create a new branch is quick, simple and good.
A1 BRANCH: added by michael
Added by Bob. on 2017.10.19
-- fix bug --
--　current working ---
2017.10.19: test igrnore file