Lesson 4. Guided Activity on Version Control with Git/GitHub


In this lesson, you will learn how to implement version control using Git and GitHub.

Learning Objectives

After completing this lesson, you will be able to:

  • Explain how Git and GitHub are used to implement version control
  • Use Git to add and commit changed files
  • Use Git to push changed files from your local computer to the repository on Github.com

What You Need

Before completing this lesson and the challenges, be sure that you have forked and cloned the repository for Homework 1. If you have not, first complete the challenge posted at the bottom of the lesson on Get Files From GitHub.

Be sure that you have also completed the lesson on Manage Jupyter Notebook Files and Markdown in Jupyter Notebook.

You will also need a web browser and your Github.com login (username and password).

Git and GitHub Workflow For Version Control

In the lesson on getting files from GitHub, you learned how to fork and clone existing GitHub repositories to make copies of other users’ repositories and download them to your computer.

In this lesson, you expand on those skills to:

  • check the status of changed files in a repository
  • add changed files to version control tracking
  • commit the changed files to your local repository
  • push those changed files from the local copy of a repository to the cloud (Github.com)

In later lessons, you will expand on this version control workflow to notify others (your collaborators) about changes you have made and that you would like to add to the original (master) copy of a repository.

Configure Git Settings On Your Computer:

  1. In the terminal, set your Github.com username by typing: git config --global user.name "Your UserName".

  2. In the terminal, set the email for your Github.com account by typing: git config --global user.email "youremail@email.com".

Note that you only have to configure these settings once on your computer. You can check your config settings for user.name and user.email using the following commands:

git config user.name or git config user.email

Make Changes to Files and Directories

Begin by using Shell to navigate to your forked repository (the ea-bootcamp-hw-1-yourusername directory) and launching Jupyter Notebook.

Open the Jupyter Notebook file for Homework 1 (ea-bootcamp-hw-1.ipynb) and make some changes.

  • If you previously started working on Homework 1 or complete the optional challenge from the previous lesson on Markdown, then you already have some changes that can be added to version control and pushed to GitHub.

  • If you have not modified Homework 1, you can make a simple change in Jupyter Notebook to add a new Markdown cell below the existing cells and include:

    • A title for the notebook (e.g. Earth Analytics Bootcamp - Homework 1)
    • A bullet list with:
      • A bold word for Author: and then add text for your name.
      • A bold word for Date: and then add text for today’s date.

Check the Status of Changes

In the terminal, navigate to your ea-bootcamp-hw-1-yourusername repository that you forked and cloned to your computer.

Run the command git status to check that changes have been made to your files that have not been pushed back to GitHub.

git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

	modified:   ea-bootcamp-hw-1.ipynb
    
no changes added to commit (use "git add" and/or "git commit -a")

The output from git status indicates that you have modified the file ea-bootcamp-hw-1.ipynb.

To keep track changes to this file, you need to:

  1. add the changes, and then
  2. commit the changes.

Add and Commit Changed Files

You will use the add and commit functions to add and commit your changed files.

  • git add: takes a modified file in your working directory and places the modified version in a staging area.

  • git commit: takes everything from the staging area and makes a permanent snapshot of the current state of your repository that is associated with a unique identifier.

These two commands make up the bulk of many workflows that use git for version control.

Modified files are staged using git add, and following a commit, all files in the staging area are snapshotted and become part of the repository's history, receiving a unique SHA-1 hash identifier. Source: Max Joseph, adapted from Pro Git by Chacon and Straub (2014).
Modified files are staged using git add, and following a commit, all files in the staging area are snapshotted and become part of the repository's history, receiving a unique SHA-1 hash identifier. Source: Max Joseph, adapted from Pro Git by Chacon and Straub (2014).

Add Files

You can add an individual file or groups of files to git tracking. To add a single file, use:

git add file-name.extension.

For example, to add the ea-bootcamp-hw-1.ipynb file that you just modified, you’d use:

git add ea-bootcamp-hw-1.ipynb.

You can also add all of the files that you have edited at the same time using:

git add .

However, use git add . with caution. Be sure to review the results from git status carefully before using git add .. You do not want to accidentally add files that you do not want to change in the GitHub repository.

Commit Files

Once you are ready to make a snapshot of the current state of your repository, you can use git commit.

The git commit command requires a commit message that describes the snapshot (i.e. changes) that you made in that commit. A commit message should outline what changed and why. These messages:

  1. help collaborators and your future self understand what was changed and why
  2. allow you and your collaborators to find (and undo if necessary) changes that were previously made.

Since you are not committing a lot of changes, you can create a short one line commit message using the -m flag:

git commit -m "Update title and author name in homework 1"

You will learn about including longer commit messages later in this course.

Push Changed Files to GitHub

So far we have only modified our local copy of the repository. To update the files in your GitHub repository, you need to push the changed files to GitHub.

You can push your changes to GitHub with:

git push origin master

You will then be prompted for your Github.com username and password.

After you have pushed your commits, visit your repository on https://github.com/yourusername/ea-bootcamp-hw-1-yourusername and notice that your changes are reflected there. Also notice that you have access to the full commit history for your repository!

Optional Challenge 1

Rename your Homework 1 file and update it on GitHub!

  1. Practice your Jupyter Notebook skills to rename your Jupyter Notebook file for Homework 1 (ea-bootcamp-hw-1.ipynb) by adding your first initial and last name to the filename (e.g. jpalomino-ea-bootcamp-hw-1.ipynb).

  2. Use your new Git skills to add and commit the changes and then push the changes to your ea-bootcamp-hw-1-yourusername repository on GitHub.

  3. Visit your repository on Github.com and see your change! What happened to the original file ea-bootcamp-hw-1.ipynb?

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