How to get started with version control and Git. From the installation to the first commit.

Git basics

Where to get it and installation

• only the command-line version includes all features

Linux

Install it via your package manager: $ sudo apt install git-all

macOS

Open a console and enter: $ git --version It is either installed already or, it will prompt you to install it.

Windows

Download the Windows installer or the Windows Portable version from https://git-scm.com/download/win

Graphical user interfaces

Have a look at: https://git-scm.com/downloads/guis/

• Looks promising, but I never used GitHub Desktop (free, commercial, macOS, Win)
• I use from time to time GitKraken ( free for students , commercial, Linux, macOS, Win)

Getting started

First-time, only

Give Git your name and e-mail address. Both will be part of your git commits so its possible to distinguish between the commits of different contributors.

git config --global user.name "John Doe"
git config --global user.email johndoe@example.com

If you want to use a different text editor, e.g. gedit: git config --global core.editor gedit Windows example: git config --global core.editor "'C:/Program Files/Notepad++/notepad++.exe' -multiInst -notabbar -nosession -noPlugin"

Check ypur settings: git config --list

Getting a Git Repository

(this section is copy’n’pasted from Chapter 2.1 Git Basics )

You typically obtain a Git repository in one of two ways:

1. You can take a local directory that is currently not under version control, and turn it into a Git repository, or

2. You can clone an existing Git repository from elsewhere.

In either case, you end up with a Git repository on your local machine, ready for work.

Initializing a Repository in an Existing Directory

If you have a project directory that is currently not under version control and you want to start controlling it with Git, you first need to go to that project’s directory. If you’ve never done this, it looks a little different depending on which system you’re running:

for Linux:

$ cd /home/user/my_project

for macOS:

$ cd /Users/user/my_project

for Windows:

$ cd /c/user/my_project

and type:

$ git init

This creates a new subdirectory named .git that contains all of your necessary repository files — a Git repository skeleton. At this point, nothing in your project is tracked yet. (See Git Internals for more information about exactly what files are contained in the .git directory you just created.)

If you want to start version-controlling existing files (as opposed to an empty directory), you should probably begin tracking those files and do an initial commit. You can accomplish that with a few git add commands that specify the files you want to track, followed by a git commit:

$ git add *.c
$ git add LICENSE
$ git commit -m 'initial project version'

We’ll go over what these commands do in just a minute. At this point, you have a Git repository with tracked files and an initial commit.

Cloning an Existing Repository

[…]

You clone a repository with git clone <url>. For example, if you want to clone the Git linkable library called libgit2, you can do so like this:

$ git clone https://github.com/libgit2/libgit2

That creates a directory named libgit2, initializes a .git directory inside it, pulls down all the data for that repository, and checks out a working copy of the latest version. If you go into the new libgit2 directory that was just created, you’ll see the project files in there, ready to be worked on or used.

If you want to clone the repository into a directory named something other than libgit2, you can specify the new directory name as an additional argument:

$ git clone https://github.com/libgit2/libgit2 mylibgit

That command does the same thing as the previous one, but the target directory is called mylibgit.

Git has a number of different transfer protocols you can use. The previous example uses the https:// protocol, but you may also see git:// or user@server:path/to/repo.git, which uses the SSH transfer protocol. […]

(end of copy’n’pasted content)

The .gitignore file

You want to track the relevant files, only. In particular, you want to avoid tracking automatically generated or system-specific files, like the *.pro.user file or the build-* folder in Qt projects. This is done with a simple text file directly in your repository folder (not the .git folder). The file name is .gitignore, with no file extension.

Creating a .gitignore file is usually one of the first steps after creating a new repository. You can write the files or file patterns which should be ignored line-by-line in the .gitignore file. It is often handy to start from an existing .gitignore file and adapt it to your needs. There is a collection of different .gitignore files at GitHub github.com/github/gitignore or you can try the .gitignore generator at gitignore.io.

Using Git

git status to get an overview of your repository git add stage a file for commit git add . stage all new or modified files git commit commit all files that are staged git commit -a stage and commit a single step git commit file1 file2 just commit file1 and file2 instead of all staged files

Branches

git branch my-branch create a new branch git checkout my-branch switch to that branch (git version < 2.23) git switch my-branch switch to that branch (git version >= 2.23)

Excercises

• Download a Qt project from StudIP
• create a new repository at gitlab.gwdg.de
• follow the instructions to push your code to GitLab
• create a new branch (e.g. “dev”), switch to that branch and do some work.
• commit to the new branch and push it to GitLab (find out how to create a branch on GitLab and sync the remote branch to your local branch)
• switch back to the master branch and merge dev into master
• push to the remote repository

Useful Links

https://ndpsoftware.com/git-cheatsheet.html

https://rogerdudler.github.io/git-guide/

https://guides.github.com/introduction/git-handbook/

http://marklodato.github.io/visual-git-guide

https://git-scm.com/doc

https://git-scm.com/book/en/v2

https://www.atlassian.com/git/tutorials/advanced-overview

https://www.atlassian.com/dam/jcr:8132028b-024f-4b6b-953e-e68fcce0c5fa/atlassian-git-cheatsheet.pdf

https://guides.github.com/