原理圖：
三個物件構成多種變化

git [common commands]

這些是在各種情況下使用的常見Git命令

start a working area

• clone Clone a repository into a new directory
  init Create an empty Git repository or reinitialize an existing one

work on the current change

• add Add file contents to the index
  mv Move or rename a file, a directory, or a symlink
  
  reset Reset current HEAD to the specified state
  rm Remove files from the working tree and from the index

examine the history and state

• bisect Use binary search to find the commit that introduced a bug
  grep Print lines matching a pattern
  log Show commit logs
  show Show various types of objects
  status
  Show the working tree status

grow, mark and tweak your common history

• branch List, create, or delete branches
  checkout Switch branches or restore working tree files
  commit Record changes to the repository
  diff Show changes between commits, commit and working tree, etc
  merge Join two or more development histories together
  
  rebase Reapply commits on top of another base tip
  tag Create, list, delete or verify a tag object signed with GPG

collaborate

• fetch Download objects and refs from another repository
  pull Fetch from and integrate with another repository or a local branch
  push Update remote refs along with associated objects