Git

What is git

Git is a is a distributed version control system: tracking changes in any set of files, usually used for coordinating work among programmers.

Basic flow of files in git

Area	Explanation
Working directory	Typically the project homefolder
Staging area	Files "staged" to go into your next commit with the git add command
Repository	The database and history of committed project files. git commit command

Install git

Download git from https://git-scm.com/download/win and install it.

Learn basic git by watching this video tutorial: Learn git in 3 hours {

Basic configuration

From terminal issue the following commands: (Windows start the git bash app)

git config --global user.name "Henrik Thomsen"
git config --global user.email "heth@mercantec.dk"

It will create a ~/.gitconfig file for the user

Create a new git project

mkdir project
cd project
git init

git init will create a .git directory

Create ssh keys for authentication

Add ssh authentication keys on Linux host and copy public key to git, then

 git remote set-url origin git@github.com:username/your-repository.git

File tracking states

A specified file can be in one of four states

State	Explanation
Untracked	The file is not tracked by git and changes are not recorded
Unmodified	The file is tracked by git and has not changed since it's last commit
Modified	The file is tracked by git and has changed since it's last commit
Staged	means that you have marked a modified file in its current version to go into your next commit snapshot.

File tracking lifecycle

Files can change state issuing git commands

Basic git commands

command	Explanation
git status	Status of git repository (must be in folder project or project subfolder)
git add <file/dir>...	Files added to the repository - Untracked->staged or Modified->staged Note: When adding a directory - the directory is not tracked for new files
git diff [file...]	See modified files content - files not staged (Use git add to stage)
git diff --staged [file...]	See staged files modified but not committed
git commit	Interactive: Commit staged files to repository - Write a comment in the editor and exit
git commit -v	Same as above, but shows you the differences
git commit -m TXT	Commits directly with the commit TXT
git commit -a -m TXT	add all changed files to the staging area and commit (Most used)
git commit --amend	Edit last commit - add files before etc....
git revert <HASH>	Revert existing commit(s)
git gui	A portable graphical interface to Git (Good diff tool)
git log	Show commit logs many options (git log [--help|-n INT|-p|--pretty=oneline|--since "5 days"|--graph])
git pull	Fetch from and integrate with another repository or a local branch.

.gitignore file

To ignore fx. build files or logfiles create a .gitignore file in the repository home directory. Content fx. *.log Pattern matching

• Asterisk matches zero or more characters *
• Patterns starting with a slash / matches in the same name as the .gitignore file
• Patterns ending with a slash / only match folder names
• Exclamation mark ! negates a pattern: fx. !henrik.log includes henrik.log even if *.log is ignored
• Nested directories: /**/*.c Will include all *.c files regardless of number if subdirectories
• See: https://github.com/github/gitignore for examples of .gitignore project files

Why is it called Git?

Linus Torvalds has quipped about the name "git", which is British English slang for a stupid or unpleasant person. Torvalds said: "I'm an egotistical bastard, and I name all my projects after myself. First 'Linux', now 'git'."

Problems

push fails due to repo has new commits pushed

If the GitHub repo has seen new commits pushed to it, while you were working locally, I would advise using:

git pull --rebase
git push

The full syntax is:

git pull --rebase origin main
git push origin main