In the world of Git, we often hear about the concepts of “Working Directory”, “Staging Area”, and “Local Repository”. They are like three different zones in Git’s “big kitchen”, each with clear divisions and working together to complete version control tasks. Understanding their relationships is the first step to mastering Git.

1. Working Directory: Your “Operating Field”¶

The working directory is the directory where you directly see and edit files. For example, when you open a project folder, all the files (including code, documents, etc.) inside it belong to the working directory.

Characteristics:
- It is a user-visible and directly operable area.
- Here, you can freely modify file contents (e.g., changing code, writing comments, adding/deleting files, etc.).

Metaphor: It’s like your home “kitchen”, where you chop vegetables and cook (modify files) and can always see the ingredients (files) in the pot.

2. Staging Area / Index: “Transfer Station” or “Refrigerator”¶

The staging area is a hidden temporary area for temporarily storing file modifications you intend to commit to the local repository. You can think of it as a “to-be-committed file list”.

Characteristics:
- It is a hidden area (usually in the .git/index file), which users cannot directly edit; operations must be performed via Git commands.
- When you run the git add command, modifications from the working directory are “staged” here.
- You can preview, modify, or undo staged content here (e.g., git reset HEAD <file> to unstage).

Metaphor: It’s like the “refrigerator” next to your “kitchen”. You temporarily store chopped vegetables (modified files) in the fridge and take them out when you confirm you want to cook that dish (commit).

3. Local Repository: “Storage Room” or “Warehouse”¶

The local repository is a hidden directory (.git) created by Git on your computer, which stores all version history, branch information, and file snapshots of the project. Think of it as a “permanent storage room for ingredients”.

Characteristics:
- It is the .git directory, containing all version control data for the project (e.g., commit history, branches, tags, etc.).
- When you run git commit, the files in the staging area are officially committed to the local repository, forming a new version.
- The local repository is the “source of truth” for the project; you can view historical versions even without an internet connection.

Metaphor: It’s like your home “storage room”, where you officially store the vegetables from the fridge (staged modifications) and can always check the ingredients you’ve stored (historical versions).

Core Relationship: “Modify → Stage → Commit” Flow¶

The essence of Git version control is managing file states across these three areas. The core daily workflow is:
Working Directory Modification → Staging Area Staging → Local Repository Commit

1. Modify Files (Working Directory)¶

Edit files in the working directory (e.g., add a line of code, correct a typo). At this point, the file status is “modified” (Git marks it as modified).

2. Stage Modifications (Staging Area)¶

Use the git add <file> command to move changes from the working directory to the staging area. Now, the staging area records your modifications, and the status becomes “staged”.
- To stage all changes, use git add . (. represents all files in the current directory).
- To unstage a specific file, run git reset HEAD <file>.

3. Commit to Local Repository¶

Execute git commit -m "Commit message" to permanently save the staged changes to the local repository. This creates a new version.

Intuitive Understanding of State Changes with an Example¶

Suppose you have a file named demo.txt with initial content Hello Git!. Here’s how the statuses change after operations:

1. Initial State:
   - Working Directory: demo.txt exists (unmodified), status: “unmodified”.
   - Staging Area: Empty (no git add has been run).
   - Local Repository: Latest version is Hello Git!.

2. Modify File (Working Directory):
   Edit demo.txt to Hello Git! This is a new version..
   Run git status:

   On branch master
   Changes not staged for commit:
     (use "git add <file>..." to update what will be committed)
     (use "git checkout -- <file>..." to discard changes in working directory)
           modified:   demo.txt

The working directory now shows modified, with no changes in the staging area.

3. Stage Modifications (Staging Area):
   Run git add demo.txt to stage the changes.
   Run git status:

   On branch master
   Changes to be committed:
     (use "git reset HEAD <file>..." to unstage)
           modified:   demo.txt

The staging area now shows staged, while the working directory remains modified (but the changes are now staged).

4. Commit to Local Repository:
   Run git commit -m "Add new version of demo.txt".
   Run git status:

   On branch master
   nothing to commit, working tree clean

All modifications are now committed to the local repository, and the status shows “clean”.

Key Summary¶

• Working Directory: Your “operating field” for direct file modifications.
• Staging Area: “Transfer station” that temporarily holds pending commits, allowing preview/undo.
• Local Repository: “Permanent storage room” that preserves all version history, the core of version control.

By understanding their relationships, you can clearly know the role of each git add and git commit command, avoiding confusion during operations. Remember: modify the working directory first, stage changes, then commit to the repository—this will help you manage code versions effectively!