git_abstraction.txt

Git is Easy

Git is three things
  Objects
  Refs
  commands - CRUD for objects and refs
  
  Shadow Directory (aka index or staging area aka what the next commit will look like)
    untracked files (files which are not in any tree object in HEAD or the shadow directory.  basically, files that git doesnt know about by name)
  
  Objects
    Blobs
    Trees
    Commits
    Tags
    
  Refs
    Branches (pointers to commits)
    Remotes (aka peers)
    HEAD (pointer to branch (or a commit in "detached HEAD" state))
  
  commands can be understood based on how the objects and refs are created, read, updated, or deleted
    add - CREATE blob objects for each file I added
          UPDATE shadow directory to account for added file(s)
    commit - CREATE tree object out of the shadow directory
             CREATE commit object that points to the previous commit (found in HEAD)
                                       points to the tree object that was just made out of the shadow directory
                                       fills in metadata about who made the commit and when
                                       fills in a message to describe the commit
             UPDATES the currently checked out branch (probably master) to point to commit it just made
    push - copies objects to a remote peer on the branch specified
    pull - copies objects from a remote peer on the branch specified
    log - READ the commit that HEAD points to through the branch HEAD refers to and to that commit's parents
    ls-files --stage - READ shadow directory and print to the console
    checkout - UPDATES HEAD
               UPDATES working directory to look like the tree that HEAD refers to (ignores untracked files)
               UPDATES the shadow directory to look like the tree that HEAD refers to
               Aborts if there are modifications in tracked files
    reset - UPDATES a branch (may leave a commit to be orphaned!)
            UPDATES the shadow directory
            --hard UPDATES the working directory (does NOT abort if there are modifications in tracked files)