Lab 1 Git Tutorial

# Interaction Programming Lab Spring 2022
## Week 1: Git Tutorial

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# Quick Git Refresher
- (Almost) linked list of "commits" which record files over time
  - Actually a tree
- Git can exist locally on your computer or on a remote server
  - Common git remotes include: GitHub, GitLab, etc.
- Android Studio provides a convenient visual git interface
  - More information [here](https://www.jetbrains.com/help/idea/using-git-integration.html)
  - You can use this for most of your git needs

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# Cloning
- To clone a repo, find the cloning link on the repository page:
  - For GitLab, it is recommended to use SSH

![:img GitLab repo cloning links, 50%](git/git_clone.png)
]
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- For these assignments, you can use Android Studio to clone your repositories.
- Using the git command line:
  ```bash
  git clone git@gitlab.cs.washington.edu:cse340-19sp/ex1-Doodle-HorribleMastiff.git
]

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# Opening Projects
- With the assignment repo cloned, open each assignment in Android studio as such
![:img Android Studio spash screen with open existing selected, 40%](git/as_open.png)

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# Opening Projects
- Once the dialog is open, navigate to the desired project folder and open.
![:img Android Studio spash screen with open existing selected, 50%](git/as_open_1.png)

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# Adding and Committing Files
- New files will appear as red in Android Studio until they are tracked
  - ![Part2Activity.java red due to not being tracked, 50%](git/git_add.png)
  - Mupliple ways to track files:
    - Right click on file, git -> add
    - From commit dialog, check file in "Unversioned Files"
- Alternatively:
```bash
git add app/src/main/java/cse340/doodle/Part2Activity.java
```

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# Adding and Committing Files
- Add files to commit
  - Specifies which changes to include in commit
- Android Studio
  - Open commit dialog (Command/Control-K)
  - Add files by checkbox
    - Can even select individual lines in files to include
  - Enter commit message

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# Adding and Committing Files
![:img Android Studio commit dialog, 50%](git/git_commit.png)

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# Adding and Committing Files
- Git command line:
```bash
git add ...
git commit -m "Add Part2Activity"
# To commit changes on all currently tracked files
git commit -am "Add a bunch of files"
# To reword a commit or add new changes
git commit --amend
```

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# Pushing
- Your git history is stored locally
- For safety and ease of use, push regularly to a remote such as GitLab
  - If you cloned an existing GitLab repository, this remote is already setup
- Git command line:
  ```bash
  # This pushes to the default remote, origin.
  git push
  # Push a new branch for the first time.
  git push -u origin branch-name
  # To push to a different branch.
  git push origin local-branch:remote-branch
  ```

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# Pushing
- In Android Studio: Command/Control-Shift-K
![:img Android Studio git push dialog, 40%](git/git_push.png)

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# Pulling: Pulls new commits from a remote such as GitLab
Two types of pulls: rebase and merge (default)

In a merge pull, if there are conflicts you will be asked to resolve them and these changes will all be put in a new "merge commit"
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Android Studio:

![:img Android Studio pull button, 60%](git/git_pull.png)

![:img Android Studio pull dialog, 55%](git/git_pull_diag.png)

- Git command line: `git pull # defaults to merge`
]
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# Using More Advanced Git commands: Rebase Merge

In a rebase merge, git attemps to interleave conflicting commits and may ask you to resolve a change multiple times. In this case, you retain better commit history

`git pull --rebase`

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# Advanced Git: Branching
- Every leaf of the git tree is given a branch name to keep track of it
- The default branch is master
]
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# Git command line
  ```bash
  # To list branches
  git branch
  # To list branches (including on remote)
  git branch -a
  # To create and checkout a new branch
  git branch -b new-branch
  # To fetch new branches.
  git fetch
  # To fetch new branches and automatically delete local branches deleted on remote.
  git fetch --prune
  # To delete branch locally
  git branch -d branch-name
  # To push deletion to remote.
  git push origin :branch-name
  ```
]

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# Branching
- Android Studio
  - Provides a convenient and intuitive interface for dealing with branches
  ![:img Android Studio git branch interface, 50%](git/git_ui.png)

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# Advanced Git: Forks
- Forking a repository allows you to start a new repository from someone else
  - What if you want to pull changes from the repository you forked?
- You can add the original repository (often referred to as the upstream) as a remote
  - `git remote add upstream {url}`
  - where url is the one used for cloning, often ssh
- To fetch changes to upstream branches:
  - `git fetch --all` or `git fetch upstream`
- To pull changes from the upstream master branch into current branch:
  - `git merge upstream/master --ff-only`
  - `git rebase upstream/master`
    - Use the optional `-i` argument after `rebase` for interactive mode
    - This allows you to delete, reorder, combine, or drop commits.
    - See here for more info [here](https://git-scm.com/book/en/v2/Git-Tools-Rewriting-History)

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# Forks
- Changes can be pulled from the upstream using the Android Studio git UI
  - However, it is possible that Android Studio may not keep upstream up-to-date
  - You can run `git fetch --all` or `git fetch upstream` to check this

![:img Android Studio git UI with rebase option for upstream/master selected, 50%](git/git_fork.png)