Git behind the scenes

Git is not magic. It is a content-addressed key-value store with a clever naming scheme on top.

The .git folder

Everything git knows lives in one directory:

Delete it and you have an ordinary folder again — with every checkpoint gone.

Objects

Git stores three kinds of thing: blobs (file contents), trees (directory listings), and commits (a tree plus metadata plus a parent).

Each is named by the SHA-1 hash of its contents, which is why the same file stored twice costs nothing.

HEAD

HEAD is a pointer to where you currently stand in history. Almost every confusing git message is really telling you that HEAD is not where you thought.