02 · Installing Git & Configuration¶

Installing Git¶

# macOS (Homebrew)
brew install git

# macOS also ships Git via Xcode Command Line Tools:
xcode-select --install

# Ubuntu/Debian
sudo apt update && sudo apt install git

# Fedora
sudo dnf install git

# Windows: download the installer from https://git-scm.com/download/win
# (this also installs "Git Bash", a Unix-like shell many Windows users prefer)

Verify the install:

git --version
# git version 2.5x.x

Any recent version (2.3x+) works fine for this course.

Telling Git who you are¶

Every commit records an author name and email. Git won't let you commit until these are set. Configure them once, globally, and they apply to every repository on your machine:

git config --global user.name "Ada Lovelace"
git config --global user.email "ada@example.com"

Use the same email you'll use for your GitHub account later — GitHub matches commit authorship to profiles by email, which is how commits show up correctly attributed to you on your GitHub profile.

Check what's set:

git config --global user.name
# Ada Lovelace

git config --list
# user.name=Ada Lovelace
# user.email=ada@example.com
# ... (plus other settings)

`--global` vs local config¶

git config --global ... writes to ~/.gitconfig — applies to every repository for your user account.
git config ... (no --global, run inside a repo) writes to .git/config in that repository only — useful if, say, your work projects need a different email than your personal ones.
Local config always overrides global config for that one repository.

# Inside a specific repo, override just for that repo:
cd ~/projects/work-repo
git config user.email "ada@company.com"

Useful config defaults worth setting¶

# Name the default branch "main" for every new repo you create
git config --global init.defaultBranch main

# Pick your default editor for commit messages (nano is beginner-friendly)
git config --global core.editor "nano"
# Or, if you use VS Code:
git config --global core.editor "code --wait"

# Make colored output the default (usually already on)
git config --global color.ui auto

# Store credentials so you're not typing a password on every push
# (macOS keeps this in Keychain automatically; on Linux/Windows:)
git config --global credential.helper cache

Where config lives¶

There are three levels, in increasing priority:

Level	Flag	File
System	`--system`	`/etc/gitconfig` (all users on the machine)
Global	`--global`	`~/.gitconfig` (your user account)
Local	(none)	`.git/config` (one specific repository)

# See exactly which file a setting came from
git config --show-origin user.name

Getting help¶

Git's built-in help is thorough and always matches the version installed:

git help commit        # opens the full manual page
git commit --help      # same thing
git commit -h          # quick usage summary

Worked example: a fresh machine, end to end¶

$ git --version
git version 2.43.0

$ git config --global user.name "Ada Lovelace"
$ git config --global user.email "ada@example.com"
$ git config --global init.defaultBranch main

$ git config --list --global
user.name=Ada Lovelace
user.email=ada@example.com
init.defaultbranch=main

That's the entire one-time setup — from here on, every git init on this machine creates a main branch by default, and every commit is correctly attributed to Ada.

How It Actually Works¶

git config isn't a special settings database — it's a tiny INI-format text file parser layered on plain files, and the "three levels" table above is really just three files Git reads in order and merges:

git config --global user.name "..." literally opens ~/.gitconfig (creating it if needed) and writes a [user] section with a name = ... line. You can get the identical result by editing that file in any text editor — the command just avoids formatting mistakes.
When Git needs a setting (say, user.email at commit time), it reads /etc/gitconfig, then ~/.gitconfig, then .git/config in that order, and the last value it sees for a key wins. That's the entire mechanism behind "local overrides global" — there's no special-casing, just last-value-wins across three files concatenated in a fixed order. git config --show-origin works by remembering which of the three files it read each value from as it went.
Author identity matters mechanically, not just cosmetically: user.name and user.email get baked as literal text into every commit object you create (author Ada Lovelace <ada@example.com> 1699999999 +0000). Since commits are content-addressed (see the previous module), changing your configured identity does not retroactively change past commits' stored author lines — it only affects commits made from that point forward.
credential.helper works by Git shelling out to a small helper program (git-credential-cache, git-credential-osxkeychain, etc.) over a tiny stdin/stdout protocol (get/store/erase with key=value pairs) each time it needs credentials for a remote — Git itself never persists your password; it delegates that entirely to the OS credential store or an in-memory cache daemon.

Exercise¶

Install Git if you haven't already, then set your global user.name and user.email to your own details (use the email you plan to sign up to GitHub with in module 7). Set init.defaultBranch to main. Finally, run git config --list --global and confirm all three values appear correctly.