Session 2 · Installing and configuring Git#

The big idea#

Before your first commit you tell Git who you are, because every commit is stamped with a name and email. Git keeps settings at three levels (system, global, local); the most specific level wins. You set your identity once globally, and override it in any project that needs a different one.

Everyday example: a visiting card and an office ID. Your personal card (global) has your own name and email. When you work on a client’s project you might hand over the client-issued ID (local) instead. Git uses the more specific one for that project.

Git settings: three levels System settings apply to every user, global settings to you, and local settings to one repository. The most specific level wins. system /etc/gitconfig everyone on this computer global ~/.gitconfig you, in every repository local .git/config this repository only more specific wins: local > global > system
System settings apply to every user, global settings to you, and local settings to one repository. The most specific level wins.

Install Git#

System

Command

Ubuntu / Debian

sudo apt install git

macOS

brew install git (or install Xcode command line tools)

Windows

Download Git for Windows from git-scm.com

Check it worked with git --version. Full instructions for every system are in the official Pro Git book.

Set your identity, and override it for one project#

02-config.sh sets a global identity, then makes a project that uses a different one. It runs in a throwaway home folder, so your real settings are never touched.

git --version

echo '--- 1. global identity, used by every repository on this computer'
git config --global user.name "DevUser"
git config --global user.email "devuser@example.com"
git config --global init.defaultBranch main
git config --global --list

echo '--- 2. a project that must use a different identity'
git init -q MyProject
cd MyProject
git config user.name "ProjectUser"
git config user.email "projectuser@example.com"

echo '--- who wins inside this project? (and where each value comes from)'
git config --show-origin --get-regexp '^user\.'
echo '--- the value Git will really use'
git config user.name

echo '--- the identity lands on every commit'
git commit -q --allow-empty -m "First commit"
git log -1 --format='%an <%ae>'

git version 2.34.1
--- 1. global identity, used by every repository on this computer
user.name=DevUser
user.email=devuser@example.com
init.defaultbranch=main
--- 2. a project that must use a different identity
--- who wins inside this project? (and where each value comes from)
file:~/.gitconfig	user.name DevUser
file:~/.gitconfig	user.email devuser@example.com
file:.git/config	user.name ProjectUser
file:.git/config	user.email projectuser@example.com
--- the value Git will really use
ProjectUser
--- the identity lands on every commit
ProjectUser <projectuser@example.com>

Reading the output:

  • --global wrote to ~/.gitconfig. git config --global --list shows the three keys we set (Git prints key names in lower case).

  • No flag inside a repository writes to that repository’s .git/config: the local level.

  • --show-origin reveals where each value comes from. The project has both DevUser (global) and ProjectUser (local); the later, more specific one wins.

  • git config user.name prints the winning value, ProjectUser.

  • The commit is stamped ProjectUser <projectuser@example.com>, proving which identity was used.

Other settings worth knowing#

Setting

What it does

init.defaultBranch main

Name the first branch main instead of master

core.editor "code --wait"

Choose the editor for commit messages

pull.rebase false

Make git pull merge (avoids a warning)

alias.st status

Type git st instead of git status

Common mistakes#

  • Skipping the identity. Git refuses to commit (“Please tell me who you are”) or guesses a wrong name from your computer.

  • Using a work email in personal projects, or the reverse. Set a local override per project.

  • Typos in --global versus local. Forgetting --global inside a repository sets it for that project only, and outside any repository it fails.

  • Changing the identity and expecting old commits to change. Settings apply to new commits only.

  • Putting secrets in config. .git/config and ~/.gitconfig are plain text files.

Hands-on exercises#

Exercise 1. Set your name and email globally and print them back.

Solution 
git config --global user.name "Your Name"
git config --global user.email "you@example.com"
git config --global user.name
git config --global user.email

The last two commands print what you just set.

Exercise 2. Make a repository whose commits use Team Bot <bot@example.com> without changing your global identity.

Solution 
git init bot-project && cd bot-project
git config user.name "Team Bot"
git config user.email "bot@example.com"
git commit --allow-empty -m "test"
git log -1 --format='%an <%ae>'

It prints Team Bot <bot@example.com>, while other repositories still use your global identity.

Exercise 3. Use git config --show-origin to find which file supplies your user.email in the current repository.

Solution 
git config --show-origin user.email

It prints the file path and the value: .git/config if you set a local override, otherwise ~/.gitconfig.

Practice#

Take the Session 2 quiz. The original Git Installation and Initial Configs page is in the reference section.