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Basic Concepts of Git#

Summary of Git Concepts#

Workspace/Stage/Repository#

• The area marked as objects in the image is the git object library, located in the ".git/objects" directory, which contains various created objects and content.
• When executing the git add command on modified/new files in the workspace, the directory tree of the stage is updated, and the content of the modified/new files in the workspace is written into a new object in objects, with the object's ID recorded in the stage's file index.
• When executing git commit, the directory tree of the stage is written into objects, updating the main branch.
• When executing the git reset HEAD command, the directory tree of the stage will be rewritten and replaced by the directory tree pointed to by the master branch, but the workspace remains unaffected.
• When executing git rm --cached “file” command, the file will be directly removed from the stage, with no changes made to the workspace.

Workspace#

Project files on the local computer.

Stage#

The stage is a temporary storage area that contains snapshots of files to be committed to the version library.
Common commands

git add filename       # Add a single file to the stage
git add .              # Add all modifications in the workspace to the stage
git status             # Check which files are in the stage

Repository#

The repository contains all version history records of the project. Each commit creates a new snapshot in the repository, which is immutable, ensuring the complete history of the project.
Common commands

git commit -m "Commit message"   # Commit changes from the stage to the local repository
git log                          # View commit history
git diff                         # View differences between the workspace and the stage
git diff --cached                # View differences between the stage and the last commit

Relationship among the three#

• Workspace -> Stage

git add

• Stage -> Repository

git commit -m "Commit message"

• Repository -> Remote Repository

git push origin branch-name

• Remote Repository -> Local Repository

git pull origin branch-name
# or
git fetch origin branch-name
git merge origin/branch-name

Git Workflow#

1. Clone the Repository#

If you want to participate in an existing project, you first need to clone the remote repository to your local machine:

git clone https://github.com/username/repo.git
cd repo

2. Create a New Branch#

To avoid developing directly on the main or master branch, it's common to create a new branch:

git checkout -b new-feature

3. Working Directory#

Edit code, add new files, or delete unnecessary files in the working directory.

4. Stage Files#

Add modified files to the stage for the next commit operation:

git add filename

Or add all modified files

git add .

5. Commit Changes#

Commit changes from the stage to the local repository and add a commit message:

git commit -m "Add new feature"

Connect to the remote repository

git remote add origin [[email protected]]

6. Pull the Latest Changes#

Before pushing local changes, it's best to pull the latest changes from the remote repository to avoid conflicts:

git pull origin main

Or if working on a new branch

git pull origin new-feature

7. Push Changes#

Push local commits to the remote repository:

git push origin new-feature

8. Delete Branch#

If the new feature branch is no longer needed, you can delete it:

git branch -d new-feature

Or delete the branch from the remote repository:

git push origin --delete new-feature

Git Commands#

Git Branches#

The interface of the Git repository after opening in fork looks like this:

You can see that each branch runs parallel to each other, and only when certain projects are completed will they be merged into the main branch.
So what is the use of branches? When planning to develop a new feature, if 50% is completed on the first day, committing directly to the master branch may prevent others from developing. If everything is written and then committed, there is a risk of losing previous progress due to unforeseen circumstances. This is where the superiority of branches comes into play. We can create a branch that is invisible to others, and developing and committing code on this branch will not affect others, allowing for free operations until development is complete, after which it can be merged into the master branch all at once.

Common Git Branch Commands#

git branch # List all local branches

git branch -r # List all remote branches

git branch -a # List all local and remote branches

git branch [new-branch-name] # Create a new branch but stay on the current branch

git checkout -b [new-branch-name] # Create a new branch and switch to it

git branch --track [branch] [remote-branch] # Create a new branch and set up tracking with the specified remote branch

git checkout [new-branch-name] # Switch to the specified branch and update the workspace

git merge [branch] # Merge the specified branch into the current branch

git branch -d [branch] # Delete the branch

git push origin --delete [branch] # Delete the remote branch