Agenda
Why use Version (Source) Control Systems
What are Gitand GitHub
Basic GitCommands
Fundamentals of GitHub
Using GitHub in Project Implementation
Why version control?
Scenario 1:
Your program is working
You change “just one thing”
Your program breaks
You change it back
Your program is still broken--why?
Has this ever happened to you?
Why version control? (part 2)
Your program worked well enough yesterday
You made a lot of improvements last night...
...but you haven't gotten them to work yet
You need to turn in your program now
Has this ever happened to you?
Version control for teams
Scenario:
You change one part of a program--it works
Your co-worker changes another part--it works
You put them together--it doesn’t work
Some change in one part must have broken something in the other part
What were all the changes?
Teams (part 2)
Scenario:
You make a number of improvements to a class
Your co-worker makes a number of differentimprovements to the sameclass
How can you merge these changes?
Version control systems
A version control system (often called a source code control system) does these things:
Keeps multiple (older and newer) versions of everything (not just source code)
Requests comments regarding every change
Allows “check in” and “check out” of files so you know which files someone else is working on
Displays differences between versions
Benefits of version control
For working by yourself:
Gives you a “time machine” for going back to earlier versions
Gives you great support for different versions (standalone, web app, etc.) of the same basic project
For working with others:
Greatly simplifies concurrent work, merging changes
What are Gitand GitHub
# Gitis a free and open source distributedversion control systemdesigned to handle everything from small to very large projects with speed and efficiency
# GitHub is aweb-basedGitrepositoryhosting service, which offers all of the distributed revision control and source code management (SCM) functionality of Gitas well as adding its own features.
How to setup Gitand GitHub
Download and install the latest version of GitHub Desktop. This will automatically install Gitand keep it up-to-date for you.
https://help.github.com/articles/set-up-git/
BASIC GIT COMMANDS
Introduce yourself to Git
On your computer, open theGitShellapplication.
Enter these lines (with appropriate changes):
gitconfig--global user.name "John Smith"
gitconfig--global user.emailjsmith@seas.upenn.edu
You only need to do this once
If you want to use a different name/email address for a particular project, you can change it for just that project
cdto the project directory
Use the above commands, but leave out the --global
The repository
Your top-level working directory contains everything about your project
The working directory probably contains many subdirectories—source code, binaries, documentation, data files, etc.
One of these subdirectories, named .git, is your repository
At any time, you can take a “snapshot” of everything (or selected things) in your project directory, and put it in your repository
This “snapshot” is called a commit object
The commit object contains (1) a set of files, (2) references to the “parents” of the commit object, and (3) a unique “SHA1” name
Commit objects do notrequire huge amounts of memory
You can work as much as you like in your working directory, but the repository isn’t updated until you commitsomething
init and the .git repository
When you said gitinitin your project directory, or when you cloned an existing project, you created a repository
The repository is a subdirectory named .gitcontaining various files
The dot indicates a “hidden” directory
You do notwork directly with the contents of that directory; various gitcommands do that for you
Making commits
You do your work in your project directory, as usual
If you create new files and/or folders, they are not trackedby Gitunless you ask it to do so
gitadd newFile1 newFolder1 newFolder2 newFile2
Committing makes a “snapshot” of everything being tracked into your repository
A message telling what you have done is required
gitcommit –m “Uncrevulatedthe conundrum bar”
gitcommit
This version opens an editor for you the enter the message
To finish, save and quit the editor
Format of the commit message
One line containing the complete summary
If more than one line, the second line must be blank
Commits and graphs
A commitis when you tell gitthat a change (or addition) you have made is ready to be included in the project
When you commit your change to git, it creates a commit object
A commit object represents the complete state of the project, including all the files in the project
The very first commit object has no “parents”
Usually, you take some commit object, make some changes, and create a new commit object; the original commit object is the parent of the new commit object
Hence, most commit objects have a single parent
You can also mergetwo commit objects to form a new one
The new commit object has two parents
Hence, commit objects forms a directed graph
Gitis all about using and manipulating this graph
Commit messages
In git, “Commits are cheap.” Do them often.
When you commit, you must provide a one-line message stating what you have done
Terrible message: “Fixed a bunch of things”
Better message: “Corrected the calculation of median scores”
Commit messages can be very helpful, to yourself as well as to your team members
You can’t say much in one line, so commit often
Typical workflow
git status
See what Gitthinks is going on
Use this frequently!
Work on your files
git add your editfiles
git commit –m “What I did”
GitHub Desktop can Help You
GitHub is a Software as a service (SaaS) platform from Microsoft that provides Git-based repositories and DevOps tooling for developing and deploying software.
It has a wide range of integrations with other leading tools.
Git : is a version Control system git also its is Distribued Version Control System.
Two types of version control system.
1) Centralize Version Control System
2) Distributed Version Control System
What does GitHub provide?
GitHub provides a range of services for software development and deployment.
- Codespaces: Provides a cloud-hosted development environment (based on Visual Studio Code) that can be operated from within a browser or external tools. Eases cross-platform development.
- Repos: Public and private repositories based upon industry-standard Git commands.
- Actions: Allows for the creation of automation workflows. These workflows can include environment variables and customized scripts.
- Packages: The majority of the world's open-source projects are already contained in GitHub repositories. GitHub makes it easy to integrate with this code and with other third-party offerings.
- Security: Provides detailed code scanning and review features, including automated code review assignment.
What is GitHub Codespaces?
Codespaces is a cloud-based development environment that GitHub hosts. It is essentially an online implementation of Visual Studio Code.
Codespaces allows developers to work entirely in the cloud.
Codespaces even will enable developers to contribute from tablets and Chromebooks.
Because it is based on Visual Studio Code, the development environment is still rich with:
- Syntax highlighting.
- Autocomplete.
- Integrated debugging.
- Direct Git integration.
Developers can create a codespace (or multiple codespaces) for a repository. Each codespace is associated with a specific branch of a repository.
FUNDAMENTALS OF GITHUB
Introduce yourself to GitHub
Register on GitHub
https://github.com/
Authenticating to GitHub Desktop
https://help.github.com/desktop/guides/getting-started/authenticating-to-github/
Configuring Gitfor GitHub Desktop
https://help.github.com/desktop/guides/getting-started/configuring-git-for-github-desktop/
Create or add a repository to GitHub
Create a new repository on GitHub
https://help.github.com/articles/create-a-repo/
From GitHub Desktop, then Publish to GitHub
https://help.github.com/desktop/guides/contributing/adding-a-repository-from-your-local-computer-to-github-desktop/
Remember to Publish, otherwise your repository would not appear on the GitHub website.
Commit your changes on GitHub
From GitHub Website
https://help.github.com/articles/create-a-repo/
From GitHub Desktop
https://help.github.com/desktop/guides/contributing/committing-and-reviewing-changes-to-your-project/
Creating a branch for your work
A branch is a parallel version of the main line of development in the repository, or the default branch (usually master). Use branches to
> Develop features
> Fix bugs
> Safely experiment with new ideas
From the GitHub Website
https://help.github.com/articles/creating-and-deleting-branches-within-your-repository/
From the GitHub Desktop
https://help.github.com/desktop/guides/contributing/creating-a-branch-for-your-work/
Synchronizing your branch
As commits are pushed to your project on GitHub, you can keep your local copy of the project in sync with the remote repository.
https://help.github.com/desktop/guides/contributing/syncing-your-branch/
Viewing the history of your commits
When you click a commit on the commit timeline, you can see more details about the commit, including a diff of the changes the commit introduced.
Each commit shows:
>The commit message
>The time the commit was created
>The committer's username and profile photo (if available)
> The commit's SHA-1 hash (the unique ID)
Revert your commit
If you change your mind about a commit after you create it, you can revert the commit.
When you revert to a previous commit, the revert is also a commit. In addition, the original commit remains in the repository's history.
https://help.github.com/desktop/guides/contributing/reverting-a-commit/
Fork & Pull: A Collaborative model
A fork is a copy of a repository that you manage. Forks let you make changes to a project without affecting the original repository. You can fetch updates from or submit changes to the original repository with pull requests.
A great example of using forks to propose changes is for bug fixes. Rather than logging an issue for a bug you've found, you can:
Fork the repository.
Make the fix.
Submit apull requestto the project owner.
Using GitHub in Project Implementation
In the section of project implementation in your project report, you may describe:
How you use GitHub in your project.
How version control helps your quality management.
How you collaborate with your teammate in GitHub.
References
Some content of the slides are adapted from
https://help.github.com/desktop/guides/getting-started/
https://help.github.com/desktop/guides/contributing/
https://help.github.com/categories/collaborating/
http://www.cis.upenn.edu/~matuszek/cit591-2012/Lectures/git.ppt
Full course on YouTube
https://youtu.be/fNYwmqKvW4g?si=CnkYZeHR3Suzb3G3
