Master Git: Essential Commands, Workflows, and Advanced Techniques

Basic Usage

The four commands copy files between the working directory, staging area (index), and repository. git add <em>files</em> – add files to the staging area. git commit – create a snapshot from the staging area. git reset -- <em>files</em> – undo the last git add <em>files</em>; git reset removes all staged files. git checkout -- <em>files</em> – discard local changes by copying from the index to the working directory.

You can also use interactive modes: git reset -p, git checkout -p, git add -p. git commit -a stages all modified files and commits them. git commit <em>files</em> commits staged files and the current working directory snapshot. git checkout HEAD -- <em>files</em> rolls back to the last commit.

Conventions

Images illustrate commit IDs, branches, and HEAD.

Command Details

Diff

Various ways to view changes between commits; examples shown.

Commit

Git creates a new commit from the staged files, sets the parent, and moves the current branch pointer.

Amending a commit with git commit --amend creates a new commit with the same parent, discarding the old one.

Checkout

Copies files from a commit or the index to the working directory and can switch branches.

Examples: git checkout HEAD~ foo.c, git checkout v1.6.6.1, git checkout main.

Detached HEAD occurs when checking out a commit, tag, or SHA directly.

HEAD in detached state

Commits made in detached HEAD are not referenced by any named branch and may be lost unless a new branch is created with git checkout -b <em>name</em>.

Reset

git reset

moves the current branch pointer and optionally updates the working directory and index with --hard or --soft.

Merge

Combines branches; fast‑forward occurs when the current branch is an ancestor of the other.

Cherry Pick

Copies a specific commit onto the current branch.

Rebase

Reapplies commits from one branch onto another, creating a linear history; similar to an automated cherry‑pick.

Use --onto to limit the range, and git rebase --interactive for complex operations.

Technical Details

File contents are stored as blobs in .git/objects identified by SHA‑1 hashes; the index lists these blobs. Commits store a tree object representing the directory structure. Detached HEAD commits are referenced only by the reflog and may be garbage‑collected.