file status life circle
basic：
modified：
Examples：
untracked:
unmodified:
modified：
Git branching ( $ git branch : view all the branches)
create a branch : $ git branch <branch name>
switching from branch to branch : $ git checkout <branch name>
moving in the previous branch : $ git checkout -
switching to a branch while creating it : $ git checkout -b <new branch's name>
merge branches :
$ git merge <branch to merge> ：merge branch to current branch
$ git merge <branch1> <branch2> : merge b1、b2 into current branch
delete a branch : $ git branch -d <branch's name>
Avoid two things:
1. Working hard on the same files on different branches.
2. Rarely merge branches
View the history
$ git log