git Tutorial

, 2012-08-08, …, 2014-03-08

This page is beginner tutorial of using the git. Git is a version control system. This tutorial focus on the most important, basic commands, one that you need to use every day. I assume you have basic experience with Linux shell/bash. 〔☛ Linux Tutorial by Example: Most Frequently Used Shell Commands〕

If you don't have git installed, on Ubuntu Linux, do sudo apt-get install git.

Then, you should setup a default name and email. It'll be used as info when you commit.

# set up default name and email
git config --global user.name "Mary Lee"
git config --global user.email "mary@example.com"

the above will create a file at ~/.gitconfig. You can run these commands again to change. (you can also edit the file directly.)

Basic Git Commands

What commands are available?

Type git help to get a list of commonly used git commands.

Here's the most commonly used commands. Those with a ★ are use daily. You can ignore others for now.

git Commands for New Project
Command Name	Mostly Used For
`git init`	Create a empty git repository in current dir. This will create a `.git` dir in current dir.
`git clone url`	Clone (like svn “checkout”) the repository from `url` to current dir.

Most Commonly Used git Commands for Changes in Local Repository
Command Name	Mostly Used For
★ `git add .`	Add changes from current dir to local repository's staging area.
★ `git commit -m"message"`	commit changes after add, to local repository. The `message` is a short description of changes you made.
`git checkout filename`	This is like svn's “revert”, update the file `filename` from last committed version from your local repo.

Most Commonly Used git Commands for Getting Info
Command Name	Mostly Used For
★ `git status`	Show the working tree status
`git log`	Show commit logs
`git diff`	Show changes between commits, commit and working tree, etc

Most Commonly Used Git Commands for Sync with Remote Repository
Command Name	Mostly Used For
★ `git pull`	Pull from remote to your local repository.
★ `git push`	Push your local repository to remote.

Creating Project

How to create a project?

cd to your source code dir, then:

git init → create a 〔.git〕 dir in the current dir. This dir holds all git's data.
git add . → add current dir (and subdir) files into git staging area.
git commit -m"first commit" → commit to local repository.

Example:

# cd to the dir containing your code
cd my_project

# initialize. This creates a .git dir.
git init

# add all files to “staging area”
git add .

# commit to local repository.
git commit . -m"my first commit"

Git will create a dir named .git in the same dir. This dir is used by git for all its info, including its database.

Adding 20k files takes ≈6 minutes. Commiting 20k files takes 6 minutes.

Clone a Project (similar to svn's “checkout”)

How to clone a project?

cd to a directory where you want the files to be (⁖ ~/mygit/), then git clone path or url. Examples:

# get a copy of git source code (≈10MB)
git clone git://git.kernel.org/pub/scm/git/git.git

# get a copy of ErgoEmacs source code (≈18MB)
git clone https://code.google.com/p/ergoemacs/

git clone URL → creates a dir in the current dir. The dir will have the same name as the project name of the remote repository at URL.

Note to svn users: git also has a “checkout” command. It's used for updating/reverting your current dir from a repository (a older version, or different branch, etc.). git checkout is similar to svn merge and svn revert.

Commit a File

See: Commit Files

Pull (Get Update) from Remote Repository

See: Get Update from Remote Repository: git pull

Revert from Local Repository

How to revert a file?

git checkout -- file name

This will update the file file name in working directory. It'll be from your local repository. Effectively, revert whatever you've done to the file.

How to revert to a particular version?

git checkout v1.2.3 -- file name         # tag v1.2.3
git checkout stable -- file name         # stable branch
git checkout origin/master -- file name  # upstream master
git checkout HEAD -- file name           # the version from the most recent commit
git checkout HEAD^ -- file name          # the version before the most recent commit

〔How do I revert one file to the last commit in git? 2009-03-28 By Brian Campbell. @ stackoverflow.com…〕

Git Ignore File

You can set git to ignore some files, such as emacs backup files, compiled files.

Each git project dir top level should have a ignore file file named .gitignore. This file contains file name patterns that git should ignore (⁖ emacs backup files, compiled files, ….)

Here's a sample content of git ignore file:

#-------------------
# emacs
*~
*.elc
[#]*[#]

#-------------------
# compiled files
*.com
*.class
*.dll
*.exe
*.o
*.so

#-------------------
# packed files
*.7z
*.dmg
*.gz
*.iso
*.jar
*.rar
*.tar
*.zip

#-------------------
# Logs and databases
*.log
*.sql
*.sqlite

#-------------------
# OS junk
.DS_Store
._*
.Spotlight-V100
.Trashes
Thumbs.db

For detail, see git help gitignore.

Commit History/Log

How to get a history of commits?

Use git log. Example of git log output:

◆ git log
commit a6205ee19e5dd0c049b7fff35de0d09189077594
Author: Xah Lee <xah@xahlee.org>
Date:   Sat Dec 22 04:14:11 2012 -0800

    fixed bug 324

commit c40dc81c7d6ca3d8ad3a4b9996a5b4ed4b0c6d08
Author: Xah Lee <xah@xahlee.org>
Date:   Fri Dec 21 22:29:28 2012 -0800

    changed getinput to not take parameters

Use git log -3 to show just last 3 commits.

This command is important because it shows the ID for each commit. You'll need to use the ID when doing comparisons or diff or revert.

git diff Between {Working Dir, Staged Area, Last Commit}

See: Git: Find Difference Between {Working Dir, Staged Area, Last Commit}, or 2 Commits

git Frequently Asked Questions

How to Branch

Git Branching Tutorial

Tagging Files

How to tag a version?

git tag "version number or any label"

This will tag the current state of your local repository. (not the index/“staging area”) You probably want to do a commit before you tag.

Setting up git on GitHub, Google Code, GitCafe

Git in Emacs

See: Emacs: magit-mode Tutorial