Git

Git is a source code management system that can save snapshots of your project on one or more branching paths.

Installation

On Debian based systems:

sudo apt install git

Glossary

• Repository: Files, folders, objects, and branches representing a project, managed within a .git folder
• Working Directory: Currently active project files and folders.
• Staging Area: Area between Working Directory and Repository where project changes are added before the next commit.
• Commit: Snapshot of staged changes from a working directory.
• Branch: Named pointer to a commit in git history.
• Head: Special pointer to the current branch.
• Remote: Link to synchronized external repository, usually on a service like GitHub.
• .gitignore: Text file listing what to ignore when moving working directory files into staging.

Flow

After initializing a new git repository in a working directory (git init) its files and folders must be added to its staging area (git add [files]) before they can be saved (git commit).

New changes in the working directory must be staged and then committed again. New branches can be created or users can switch to an existing branch (git checkout) to explore divergant changes, then eventually combined (git merge).

If a local repository is linked to a remote repository, changes made locally can be copied to the remote location (git push), and changes in the remote repository can be copied down to the local version (git pull).

Example commands

# Initialize a git project
git init

# Add specific files and folders
git add <FILE NAME>

# Commit staged changes with a message
git commit -m "<YOUR MESSAGE>"

# List all branches
git branch

# Checkout an existing branch
git checkout <BRANCH NAME>

# Reset code back to last commit
git reset --hard

# Checkout a new branch based on current branch
git checkout -b <BRANCH NAME>

# Stash outstanding changes (to cleanly switch branches)
git stash

# Retrieve previously stashed changes
git stash pop

Remote Repositories

Cloud services like GitHub, GitLab, and BitBucket host git servers which can be synchronized with local repositories. When an existing project on these services is cloned, its .git directory will include a remote link to the original project, commonly known as origin.

A local repository can also be synchronized in the opposite direction, copying a local project to an empty repository on a cloud server.

# Create remote link named 'origin'
git remote add origin <REMOTE URL>

# Push local master branch to origin master branch
git push -u origin master

# Copy remote git repository to local folder
git clone <REMOTE URL>

Pull Requests

On remote git server services like GitHub, other users are able to “fork” a repository, which creates a copy of that project on their own account. If a user clones the repository and pushes changes, they may open a “pull request” back to the original project, requesting a review of their work and to either accept or deny merging these changes.

GitHub Pull Request Tutorial