* initial a new repo
    * git init
* add file to buffer 
    *  git add filename
* add the file (in buffer) to repo
    * git commit -m "description"
* move to one version
    * git reset --hard commit_id
    * git reset --hard ^HEAD
* see submit history
    * git log
* see command history
    * git reflog
* discard file modification
    * git checkout -- filename
* discard file in buffer
    * git reset HEAD filename
    * git checkout -- filename
* see differences between the index file and the current HEAD commit
    * git status
* delete a file
    * git rm
* link a remote repo
    * git remote add origin git@server-name:path/repo-name.git
* first time update master branch
    * git push -u origin master
* update  master branch to remote
    * git push origin master
* About branch
    * see branch
        * git branch
    * create a new branch
        * git branch branchname
    * move to a branch
        * git checkout branchname
    * create & move to a branch
        * git checkout -b branchname
    * merge a branch to present branch
        * git merge branchname
        * git merge --no-ff -m "description" branchname(no fast forward)
    * delete branch
        * git branch -d branchname
        * git branch -D branchname(delete anyway)
* see branch merge graph
    * git log --graph( --pretty=oneline --abbrev-commit)
* record the current state
    * git stash
* see stash lists
    * git stash list
* recover stash
    * git stash apply
* delete stash
    * git stash drop
* recover & delete stash
    * git stash pop
* merge changes from remote to current
    * git pull
* see remote repo information
    * git remote -v
* About tag
    * create a new tag
        * git tag tagname
        * git tag -a tagname -m "description"
    * list tag
        * git tag
    * push a tag
        * git push origin tagname
    * push all tags
        * git push origin --tags
    * delete a local tag
        * git tag -d tagname
    * delete a reomote tag
        * git push origin :refs/tags/tagname