basic

1. .git directory
2. staging Area
3. Working Directory

git rm

just like
    1.rm file
    2.git add file

git add revert

1.modify or add revert
    git reset file

2.git rm revert
    git checkout HEAD file

3.git rm revert all change 
    git reset --hard

git rm --cached

to ignore some had commit but now you want to ignore,something you not add in .gitignore file

    git rm --cached file

    #the file from staging Area to delete and became untrace state

git log

    # show last one log,-p show ditail , -1 limit count
    1.git log -p -1

    # show just this file's change log
    1.1 git log -p file

    # show counting for log(3 file modify,100 line code new add,40 line deleted)
    2.git log --stat

    #show oneline ,maybe useful
    3.git log --pretty=oneline

    #since limit time
    4.git log --since=2.weeks
      git log --since=7.months

    #show brach graph,Head point,braches
    5.git log --decorate --oneline --graph --all 
    git config --global alias.lga 'log --decorate --oneline --graph --all'

git log limit

    1.time --after,--before
    2.--commiter="sha1 checksum"
    3.--author='author name'
    4. -(n) limt num
    5.--grep 'commit message'
    6 -S 'adding or removing code matching the string'

git commit undo

    git commit --amend

git checkout undo

    # modify a file ,before use git add,if you want to revert the file
    git checkout file