Master Git from Scratch: Essential Commands and Workflows

Basic Concepts

Git is a free, open‑source, distributed version‑control system that records file changes in a repository. Each file maintains a complete history, and the repository stores all commits.

Installation

sudo apt‑update
sudo apt‑get install git
git --version

Workflow

Git uses three areas when managing a project: the working directory, the staging area (index), and the local repository. The local repository consists of three "trees":

Working Directory : holds the actual files.

Staging Area (Index) : a cache that temporarily stores your changes.

Local Repository : a directory where Git tracks all file modifications, allowing you to view history or revert to any previous version. HEAD points to the latest commit.

File States

Each file in Git can be in one of three states:

Modified : the file has changes but is not yet staged.

Staged : the file is added to the next commit (using git add).

Committed : the file is safely stored in the local repository (using git commit).

Creating a Repository and the First Commit

1. Initialize Repository

git init

This creates a .git directory in the current folder.

2. Add Files

Add new files such as url.c and README.md. Use git status to see untracked files.

3. Stage Files

git add <filename>
# Add all files
git add .
# Add all C files
git add *.c

4. Commit Changes

git commit -m "Initial project version"
# Or open the editor for a message
git commit

After committing, the changes are in HEAD but not yet in a remote repository.

5. Push to Remote

git push origin master

You can replace master with any branch name. To connect a local repository to a remote server, add it first:

git remote add origin <server‑url>

Branch Operations

View Branches

git branch

Without arguments, this lists local branches. The current branch is marked with an asterisk.

Create a Branch

git branch test

A new branch named test appears alongside master.

Switch Branches

git checkout test
# Or create and switch in one step
git checkout -b test

Merge Branches

After making changes on test and committing, merge back into master:

git checkout master
git merge test

Delete a Branch

git branch -d test
# Force delete
git branch -D test

Push a Branch

git push origin <branch>

Replacing Local Changes (git checkout)

To discard local modifications to a file, use: git checkout -- <filename> This restores the file from HEAD while leaving staged changes untouched.

Resetting Commits (git reset)

Soft Reset

Moves HEAD to a specified commit without altering the working directory or index, allowing you to amend and recommit changes.

Hard Reset

Resets the working directory, index, and HEAD to a previous commit, discarding all subsequent changes.

Reverting Commits (git revert)

Creates a new commit that undoes the changes introduced by a specific commit, preserving history.

git revert 209485

Cherry‑Picking Commits (git cherry-pick)

To apply a specific commit from another branch onto the current branch:

git branch cherry
git checkout cherry
# make some commits on cherry
git checkout master
git cherry-pick b98fc77

This copies the selected commit onto master, creating a new commit that contains the same changes.