Git Basics

Overview

What is Git?

Software for tracking changes in files

Helps coordinate distributed work for developers, released in 2005.
It’s open source and free and in it’s current form enables collaboration, revision management, debugging, CI/CD etc.
Before GIT became ubiquitous, SVN Apache Subversion or BitKeeper (paid) were used

Linus Trovolda

Creator of Linux, wrote Git
Linux is a Kernel written in 1991 - vast majority of webservers are Unix/Linux based
Key features led to high user adoption - free, stable, secure, multi-user (distributed)
Apparently he unplugged, went away in a cabin and didn’t leave until it was written, made it available for free
Here’s a (70 minute) talk he gave at Google (2007), about Git

Why is it called Git?

Over 40 acronmyms for GIT - all true

Linus says he likes to name things after himself (like Linux) - but the more likely explanation is git was sufficiently quirky and not a pre-existing Linux command

Github.com (Estb. 2007)

leverage and added “social” elements to Git - a GUI, public + private + opensource code, a news feed, a graphical commit history

Github Pages (blog/personal websites), Github Gists (code snippet sharing)
word to the wise - they also have access to all your sourcecode, if you’re into privacy. MSFT paid ~$8 billion for a reason

Github Alternatives

GitLab(open core), Bitbucket (By Atlassian), GitoLite (self hosted, access control layer on top of Git)

Github w/ JIRA/Trello (Agile SDLC)

Git/Github Terms

Repository

Repository (repo) - root folder of application (code)
Remote Repo - hosted on a remote registry - aka upstream repo like GH, GitLab etc
Repo on your device (local repo aka locally)

User/Collaborator

multiple people can work on that code (engineers, QA etc)
git config --global user.name "Mona Lisa"

Organization

Trello, Docker … nyu-csci-ua-0467-001-fall-2021

Teams

Cluster of users
Let’s say Google Docs has one team of 8 developers and 16 QA engineers
We have an org. nyu-csci-ua-0467-001-fall-2021 the org has one repo each for the weeks HW, and org has each of you added as a team + user. Why? So you can potentially add other users into the team for collaboration (not required)

Issues

forum like place to commment/report on bugs/RFC (esp useful in opensource/public libraries/packages)
e.g. npm version x not compatible with new macOS update

Git locally, brew install git

if you’re on a mac and have brew, brew install git
else download it
check if it’s installed git --version

git version 2.21.0 (Apple Git-122.2)

git init

mkdir git-ws-test && cd git-ws-test
git init
ls -lah

git status

touch test.js
ls
git status

Git becomes aware but doesn’t care - it’s not tracking changes in the file

git diff

you can add text into test.js but git wont track changes to it

git diff

echo 'hello world' > test.js

cat test.js

 hello world

git diff
#returns nothing

git diff test.js
#returns nothing

git add .

Until you run git add . or git add <filename>, and then make changes git won’t start tracking changes. Adding a file is also called staging (preparing) it for a commit

git add .
echo "you're added. am i being tracked?" >> test.js
cat test.js
git diff

unstage

You’re allowed to change your mind

use "git rm --cached <file>..." to unstage

git commit -m “this is a test commit (think of it as a tweet)”

You’re happy with the progress you’ve made, you want to commit to it - write a message
Some write essays in the messages - i prefer 144 characters or less (be clear + concise)
git commit -m "should be like a tweet"

git add . #the updated message
git commit -m "should be like a tweet"

git commit --amend

git push

Pushing repo without an upstream (remote) repo will give an error

git push


  fatal: No configured push destination.
  Either specify the URL from the command-line or configure a remote repository using

    git remote add <name> <url>

  and then push using the remote name

    git push <name>

github create repo

You get a repo URL - https://github.com/osehgol/git-ws-test

git remote

git remote add origin https://github.com/osehgol/git-ws-test.git
git remote -v

push in peace git push --set-upstream origin master
https://github.com/osehgol/git-ws-test

git user

git config --global user.name "Mona Lisa"

git log

git log

Is a history of your commits (squash, cherry pick, reset)

git clone git pull

Sharing code is easy

git clone https://github.com/osehgol/git-ws-test.git

once cloned - collaborator doesn’t need to git init, git remote add ... etc. s/he gets all the logs etc.

echo 'this is a collaborators input' >> test.js

git add .
git commit -m "collaborators input"
git push

Owner can now pull the change

git pull --rebase and they’ll have the updated test.js file

For this class, you don’t need --rebase just git pull would be fine

Branch

Git lets you branch out your code into separate streams (so different developers can work on it) and then merge or rebase back into the main/master branch. At this time you’re not going to need branches but here’s how you create/switch between them.

git branch
git checkout -b test_branch
git branch
git checkout master

git pull –rebase vs git pull (git fetch && git merge)

when working with others on the main/master branch a good strategy is to pull with rebase everytime you want to get some fresh stuff from upstream

git pull --rebase

Rebasing is the process of moving or combining a sequence of commits to a new base commit (git rewrites logs internally to make them clean/linear).
this avoids conflicts and re-pushing of code which happens under merge (git logs get crazy in merge)
Example of rebase - stackoverflow
Which strategy to use atlassian
Golden rule of Git rebase - never use it on public branches.

git stash

Sometimes - you’ll have local uncommited changes, but have to pull –rebase w. upstream.
Use git stash - it stashes your changes temporarily, clearing your branch for a conflict free pull --rebase, you can then git stash pop your changes back into branch OR git stash clear if the changes are redundant

vim .gitignore

tokens, keys, node_modules etc

Sample SDLC w. git

git is versatile enough for orgs to figure out their own workflow. Here’s a sample.

Cloning and working on last nights home work

git clone https://github.com/nyu-csci-ua-0467-001-fall-2021/username-homework01 cd username-homework01 ls -lah

already has .git dir in it - you’re ready to make, add (track), commit & push changes

echo 'test text' > src/connectmoji.js git add . git commit -m "git ws test" git push

we can see your work
not the rest of the class
possible to add collaborators - but each of you are individually graded (check w. Prof Joe)

Tools

Handy tools
Bash-it
SourceTree