My start of git

1install git:
    in my ubuntu     "sudo apt-get install git"
2git command:
    Generate git repository
    git init : initial a git repository

    Add file into git repository
    git add file:
    git commit -m "explain content"

    Check the state of repository
    git status

    Check the change of file
    git diff

    Check the change log
    git log

    Change version
    git reset --hard commit_id
        help command:
        git log :check the commit log
        git reflog :check the command log

    Revocation
    1)when you change file but not add and commit you can use below command to repeal change
    git checkout -- file
    2)when you change file and add but not commit you can use below two steps to repeal change
    git reset HEAD file
    git checkout -- file
    3)When you change file and use add commit ,you can only use below command
    git reset --hard commit_id

    Delete file   
    1)when you delete file only in your work area
    rm file
    and can be repeal
    git checkout -- file
    2)when you delete file in work area and repository
    rm file
    git rm file
    git commit -m "remove file" 
    and can be repeal
    git reset --hard commit_id

    Relevance a repository on github
    git remote add origin git@server-name:path/repo-name.git

    Clone an repository from github to local host
    git clone add origin git@server-name:path/repo-name.git

    Push change to distance repository
    1)at first time
    git push -u origin master 
    2)not first time
    git push origin master

    Branch
    1)check branch
    git branch
    2)create branch
    git branch branch_name
    3)switch branch 
    git checkout branch_name
    4)create and switch branch
    git checkout -b branch_name
    5)merge other branch to current branch
    git merge other_branch_name
    6)delete branch
    git branch -d branch_name