1. Version Control with GitHub
Computer Science 209
Version Control with GitHub
Computer Science 209 1

2. What is GitHub?
A code hosting platform for version control and collaboration
Facilitates collaboration
Uses repositories, branches, commits, and Pull Requests
Available as command-line or GUI
What is GitHub?
A code hosting platform for version control and collaboration
Facilitates collaboration
Uses repositories, branches, commits, and Pull Requests
Available as command-line or GUI 2

3. Downloading GitHub Desktop
The GUI provided by GitHub
You must also make a GitHub account
Downloading GitHub Desktop
The GUI provided by GitHub
You must also make a GitHub account 3

4. Repositories A repository is usually used to organize a single project
Repositories can contain anything your project needs
Files, folders, images, etc
GitHub uses repositories as a controllable folder for your project
Repositories
A repository is usually used to organize a single project
Repositories can contain anything your project needs
Files, folders, images, etc
GitHub uses repositories as a controllable folder for your project 4

5. Creating a Repository in GitHub Desktop
Select New repository
Either on the right side of the screen or under the File menu
Name your repository
Write a short description
Select public or private accessibility
(Optionally) Select Initialize this repository with a README
Click Create Repository
Creating a Repository in GitHub Desktop
Select New repository
Either on the right side of the screen or under the File menu
Name your repository
Write a short description
Select public or private accessibility
(Optionally) Select Initialize this repository with a README
Click Create Repository 5

6. File Location
GitHub will manage the files on your local computer for you
You can access these files with Ctrl+Shift+F on windows
Edits made locally to these files will be detected by GitHub Desktop
These files will also update to your current branch of code
File Location
GitHub will manage the files on your local computer for you
You can access these files with Ctrl+Shift+F on windows
Edits made locally to these files will be detected by GitHub Desktop
These files will also update to your current branch of code 6

7. Master Branch By default the repo has one branch named master
The master branch is the "definitive branch"
Other branches are created for making edits to the master
Once satisfied with the edits, the branch is then committed to the master
In general, don't edit the master branch
Master Branch
By default the repo has one branch named master
The master branch is the "definitive branch"
Other branches are created for making edits to the master
Once satisfied with the edits, the branch is then committed to the master
In general, don't edit the master branch 7

8. Branches Have you ever saved different versions of a file?
story.txt
story-liz-edit.txt
story-liz-edit-final.txt
Branches accomplish similar goals in GitHub repositories
Creating a branch off the master branch is making a copy of master
As it was at that point in time
Branches
Have you ever saved different versions of a file?
story.txt
story-liz-edit.txt
story-liz-edit-final.txt
Branches accomplish similar goals in GitHub repositories
Creating a branch off the master branch is making a copy of master
As it was at that point in time 8

9. Making a Branch Go to your repository
Click the drop down at the top of the file list that says branch: master
Type a branch name into the new branch text box
Select the blue Create branch box or hit Enter on your keyboard
The branch will be identical to the master until edits are made
Making a Branch
Go to your repository
Click the drop down at the top of the file list that says branch: master
Type a branch name into the new branch text box
Select the blue Create branch box or hit Enter on your keyboard
The branch will be identical to the master until edits are made 9

10. Switching Branches
Selecting the drop-down menu at the top will let you switch between published branches
GitHub will automatically change the files on your local computer
Give it a little time to update on larger projects
Make sure you're on the correct branch before editing any files!
Switching Branches
Selecting the drop-down menu at the top will let you switch between published branches
GitHub will automatically change the files on your local computer
Give it a little time to update on larger projects
Make sure you're on the correct branch before editing any files! 10

11. Making Edits and Running Programs
You can use any editor of your choice on the files in the GitHub repo
It behaves just like any other folder on your computer
Same for running the code
javac, java
Saving locally will not save to the repo branch
To save to the branch you must commit the edits
Making Edits and Running Programs
You can use any editor of your choice on the files in the GitHub repo
It behaves just like any other folder on your computer
Same for running the code
javac, java
Saving locally will not save to the repo branch
To save to the branch you must commit the edits 11

12. Committing On GitHub, saved changes are called commits
Each commit has an associated commit message
A description explaining why a particular change was made
Commit messages capture the history of your changes
Other contributors can understand what you’ve done and why
Committing also shows how frequently you are working on your code
This will be important for projects 5 onwards
Committing
On GitHub, saved changes are called commits
Each commit has an associated commit message
A description explaining why a particular change was made
Commit messages capture the history of your changes
Other contributors can understand what you’ve done and why
Committing also shows how frequently you are working on your code
This will be important for projects 3-5 12

13. Edit and Commit Open the file you wish to edit Make edits
Write a commit message
Describe your changes briefly in the summary bar
More details can go in the box in the larger text box
Click the blue commit button to save to the current branch
You can select which files are committed with the checkboxes to the left of the files
Open the file you wish to edit
Make edits
Write a commit message
Describe your changes briefly in the summary bar
More details can go in the box in the larger text box
Click the blue commit button to save to the current branch
You can select which files are committed with the checkboxes to the left of the files

14. Differences
GitHub Desktop will show you a visualization of the changes made
Red means removed
Green means added
Differences
GitHub Desktop will show you a visualization of the changes made
Red means removed
Green means added 14

15. Pushing Committing will only update your local repo
Making a push request will update the repo online
So that other collaborators can see the changes
In order to finally accept the new edits as final, a pull request is needed
Push by using the blue button or typing Ctrl+P
Pushing
Committing will only update your local repo
Making a push request will update the repo online
So that other collaborators can see the changes
In order to finally accept the new edits as final, a pull request is needed
Push by using the blue button or typing Ctrl+P 15

16. Pull Requests
Pull request propose your changes to the rest of your collaborators
Requesting that someone review the code
Finally pull in your contribution and merge them into their branch
Pull requests show diffs (differences) of the content from both branches
The changes, additions, and subtractions are shown in green and red
Pull Requests
Pull request propose your changes to the rest of your collaborators
Requesting that someone review the code
Finally pull in your contribution and merge them into their branch
Pull requests show diffs (differences) of the content from both branches
The changes, additions, and subtractions are shown in green and red 16

17. More on Pulling
in your pull request message will tag that user in the request
You can even open pull requests in your own repository and merge them yourself
A great way to learn the GitHub flow before working on larger projects
More on Pulling
in your pull request message will tag that user in the request
You can even open pull requests in your own repository and merge them yourself
A great way to learn the GitHub flow before working on larger projects 17

18. How to Make a Pull Request
Click the blue "pull request" button
You must be logged in to GitHub for this page to load
If you get a 404 error, log in!
Fill out information about your edits
Click create pull request
How to Make a Pull Request
Click the blue "pull request" button
You must be logged in to GitHub for this page to load
If you get a 404 error, log in!
Fill out information about your edits
Click create pull request 18

19. Finally, Merging
When a branch is complete it’s time to bring the changes together
A branch can be considered complete when one new element is added which does not break the code
Everything still compiles, other tests do not crash, etc.
This is achieved by merging the branch into the master branch
Finally, Merging
When a branch is complete it’s time to bring the changes together
A branch can be considered complete when one new element is added which does not break the code
Everything still compiles, other tests do not crash, etc.
This is achieved by merging the branch into the master branch 19

20. How to Merge a Branch
Click the green Merge pull request button to merge the changes into master
Click Confirm merge
Delete the branch with the Delete branch button in the purple box
Since its changes have been incorporated it is no longer needed
How to Merge a Branch
Click the green Merge pull request button to merge the changes into master
Click Confirm merge
Delete the branch with the Delete branch button in the purple box
Since its changes have been incorporated it is no longer needed 20

21. Conflicts
The bane of every GitHub user's existence is conflicts between local check-outs of repos
If two people change the same file in different ways, GitHub does not know which one to use
Avoid conflicts at all costs!
Never work on the same file as another user
Communicate with your team
All else fails… nuke it
Save your edits somewhere else and check out a new copy of the master branch
Conflicts
The bane of every GitHub's existence is conflicts between local check-outs of repos
If two people change the same file in different ways, GitHub does not know which one to use
Avoid conflicts at all costs!
Never work on the same file as another user
Communicate with your team
All else fails… nuke it
Save your edits somewhere else and check out a new copy of the master branch 21