The Pieces of Git

As far as the Git work­flow is con­cerned, there are three pieces of Git that we should be aware of before mov­ing for­ward with some slight­ly more com­plex (but total­ly doable!) explanation.

They are:

• Repos­i­to­ry
• Index
• Work­ing Tree

Let’s cov­er each one in a bit more detail.

Repos­i­to­ry

A repos­i­to­ry is a col­lec­tion of com­mits, and a record of what the project’s work­ing tree looked like at one time. You can access the his­to­ry of com­mits via the Git log.

There’s always a cur­rent start­ing point in a repos­i­to­ry and that’s called the HEAD. A repos­i­to­ry also con­tains tags and branches.

The job of the repos­i­to­ry is to be the con­tain­er that tracks the changes to your project files.

Work­ing Tree

This is a direc­to­ry on your file sys­tem that is asso­ci­at­ed with a repository. 

You can think of this as the filesys­tem man­i­fes­ta­tion of the repos­i­to­ry. It’s full of the files you edit, where you add new files, and from which you remove unneed­ed files. Any changes to the Work­ing Tree are not­ed by the Index (see below), and show up as mod­i­fied files.

Index

This is a mid­dle area that sits between your Git repos­i­to­ry and your Work­ing Tree.

The Index keeps a list of the files Git is track­ing and com­pares them to your Work­ing Tree when you make changes. These changed files show up as mod­i­fied before you bun­dle them up into a commit.

You might have heard this called the stag­ing area where changes go before they are com­mit­ted to the repos­i­to­ry as com­mit objects. 

If you ever use the -a flag when com­mit­ting, then you are effec­tive­ly bypass­ing the Index by turn­ing your changes direct­ly into a com­mit with­out stag­ing them first.