GitHub, Remote and Push — and Good Commit Messages

What will we learn?#

• What GitHub is.
• What a Remote (a remote server) is and what origin is.
• How to upload code with git push.
• How to write good Commit messages.

Why do we need this?#

Until now the whole history is saved only on your computer. GitHub gives:

• A cloud backup — the laptop broke? The code is safe.
• Sharing — you send a link to the instructor, to teammates, to an employer.
• A portfolio — your GitHub profile is a developer’s professional CV. Recruiters really look at it.
• Teamwork — the whole team syncs code through the same Repository.

From today, every project in the course (including the OOP projects and the integration project) goes up to GitHub.

Explanation from the basics#

GitHub#

GitHub is a website (and service) that hosts Git Repositories on a server. It is a Server in the sense we learned in the topic on the computer, the operating system and the network: your local Git is the Client, and it sends the Commits to GitHub over HTTPS.

(There are also similar services: GitLab and Bitbucket. The idea is the same.)

Remote and origin#

Remote = the address of another copy of the Repository that is somewhere else, usually on GitHub. A Remote is given a nickname, and by convention, the main Remote is called origin.

Your computer                              GitHub
┌──────────────────────┐   git push    ┌──────────────────────┐
│ Local repository     │ ────────────► │ Remote repository    │
│ (.git, all commits)  │               │ "origin"             │
└──────────────────────┘ ◄──────────── └──────────────────────┘
                           git pull

• git push — sends the local Commits that are not on the Remote yet.
• git pull — downloads new Commits from the Remote (when someone else pushed, or when you worked from another computer). We will not go into it deeply right now.
• git clone <url> — downloads an existing Repository from GitHub to the computer, including the whole history.

Authentication#

GitHub needs to know that you are allowed to push to the Repository. On Windows and Mac, on the first push a sign-in window opens in the browser (Git Credential Manager), you sign in once, and the system remembers. GitHub does not accept the account password in the Terminal. If you are asked for a “Password” in the Terminal, you need a Personal Access Token (we will see it in the common mistakes).

Good Commit messages#

Test: complete the sentence “If applied, this commit will ___”. Add login form ✓. Added login ✗.

Syntax#

Connecting an existing local Repository to GitHub and the first push:

git remote add origin https://github.com/USERNAME/REPO-NAME.git
git branch -M main
git push -u origin main

After that, every time:

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

Helper commands:

git remote -v                  # show configured remotes
git clone https://github.com/USERNAME/REPO-NAME.git   # download an existing repo

First code example#

Uploading the calculator project from the previous lesson to GitHub, step by step:

Step 1 — an account. Go to github.com → Sign up. A professional username (it will appear on your CV!). It is recommended to use the same email you set in git config.

Step 2 — a new Repository. On the website: + (at the top) → New repository:

• Repository name: calculator
• Public (visible to everyone) or Private.
• Do not check “Add a README”, “.gitignore” or “license”. We already have a local Repository, and we want to start with an empty Remote.
• Create repository.

Step 3 — connecting and pushing. GitHub shows the commands. From the calculator folder:

git remote add origin https://github.com/dana-cohen/calculator.git
git branch -M main
git push -u origin main

Output:

Enumerating objects: 18, done.
Counting objects: 100% (18/18), done.
Delta compression using up to 8 threads
Compressing objects: 100% (16/16), done.
Writing objects: 100% (18/18), 1.92 KiB | 1.92 MiB/s, done.
Total 18 (delta 4), reused 0 (delta 0), pack-reused 0
To https://github.com/dana-cohen/calculator.git
 * [new branch]      main -> main
branch 'main' set up to track 'origin/main'.

Step 4 — checking. Refresh the Repository page on GitHub. The files are there! Click Commits to see the whole history, with the messages you wrote.

Breaking down the code line by line#

Another example#

A full work cycle after connecting — a change, a Commit, a Push, and a check on the website:

git status
git add calculator.py
git commit -m "Add power function"
git push
git status

In calculator.py:

def power(base, exponent):
    return base ** exponent

Output of git push:

To https://github.com/dana-cohen/calculator.git
   b81c0f4..e2f7a90  main -> main

Output of git status after the push:

On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

Breakdown:

• b81c0f4..e2f7a90 — the branch on GitHub “moved forward” from the previous Commit to the new one.
• Your branch is up to date with 'origin/main' — the local and the Remote are in sync. Before the push, git status would have written Your branch is ahead of 'origin/main' by 1 commit, that is, “you have a Commit that has not been uploaded yet”.
• On the website, in calculator.py, you see the new function, and in the history Add power function.

README.md — the project’s business card#

GitHub automatically shows the file README.md on the Repository’s main page. Write one in every project:

# Calculator

A simple Python calculator - Kodkod 6 intro course, week 2.

## How to run

    python main.py

## Functions

- add, subtract, multiply, divide, power

The file is written in Markdown: # = a heading, - = a list. And then: git add README.md, git commit -m "Add README", git push.

Common mistake#

Mistake 1: GitHub asks for a password in the Terminal, and the password “doesn’t work”.

remote: Support for password authentication was removed on August 13, 2021.
fatal: Authentication failed for 'https://github.com/...'

GitHub does not accept an account password in the Terminal. The recommended solution: Git for Windows and Mac come with Git Credential Manager, which opens a sign-in window in the browser. If it does not open, create a Personal Access Token: on the website → Settings → Developer settings → Personal access tokens. Paste the Token instead of the password.

Mistake 2: a Remote created with a README, and a push that is rejected.

! [rejected]        main -> main (fetch first)
error: failed to push some refs to 'https://github.com/...'
hint: Updates were rejected because the remote contains work that you do not have locally.

You checked “Add a README” when creating the Repository on the website, so GitHub has a Commit that you do not have. The simplest solution at this stage: delete the Repository on the website (Settings → Delete) and create it again empty. (The “real” solution is git pull, which we have not learned in depth yet.)

Mistake 3: remote origin already exists.

error: remote origin already exists.

You already added a Remote with this name (maybe with a wrong address). Check with git remote -v, and fix it: git remote set-url origin <correct-url>.

Mistake 4: pushing secrets. A file with a password or an API key that was pushed to a public Repository is considered leaked, even if you delete it in the next Commit, because it stays in the history. Bots scan GitHub and find keys within minutes. .gitignore before the first Commit, and secrets never in the code.

Mistake 5: a Commit without a Push. “I made a Commit, so it is on GitHub”. No! A Commit is local only, and only push uploads.

Practice#

The exercises use only what was taught in this lesson and the lessons before it. Try on your own first, and only then open the solution.

Exercise 1: Connecting to GitHub#

You created an empty Repository on GitHub at the address https://github.com/dana-cohen/calculator.git. The computer already has a local Repository with Commits. Write the commands that connect it to GitHub and upload the code for the first time.

git remote add origin https://github.com/dana-cohen/calculator.git
git branch -M main
git push -u origin main

Exercise 2: Local versus Remote#

Dana made three Commits on her computer, but did not run git push. A friend opens the Repository on GitHub.

1. Do they see the three Commits?
2. Dana’s computer broke before she ran push. What was lost?

Exercise 3: push, clone and remote#

Match each command to what it does:

git push
git clone <url>
git remote add origin <url>

(a) Downloads an existing Repository from GitHub to a new computer. (b) Sets where to upload to. (c) Uploads Commits to GitHub.

Exercise 4: Good Commit messages#

For each message — good or not? If not, write a good version.

1. fix
2. Add divide function to calculator
3. changes
4. asdf
5. Fix crash when dividing by zero

Exercise 5: The daily routine#

You added a function power to the project. Put the commands in the right order:

git push
git commit -m "Add power function"
git status
git add calculator.py

git status
git add calculator.py
git commit -m "Add power function"
git push

Summary#

• GitHub = a server that hosts Repositories in the cloud. The local Git talks to it over HTTPS.
• Remote = a remote copy. origin = the accepted nickname for the main one.
• First connection: git remote add origin <url> → git push -u origin main. After that: git push.
• Commit = local. Push = to the cloud. git status shows whether you are “ahead” of the Remote.
• A Commit message: imperative, specific, short, one change, in English. “If applied, this commit will ___”.
• Secrets are never pushed. .gitignore before the first Commit.

Official documentation#

• GitHub Docs — Creating an account
• Pro Git — Working with Remotes
• git push
• GitHub Docs — About READMEs