Git intro

This is a short practical introduction to collaborative Git fundamentals. For the theoretical part, see the slides.

Go get started:

1. Create a GitHub account.
2. Fork this repository.
3. Install Git on your computer.
4. Clone your forked repository:

git clone <your-repository-url>

Exercise 1: Commit

1. Make a change in file_1.md.
2. Check the status of the repository.

git status

3. Check the changes made in the file.

git diff

4. Add the file to the staging area.

git add file_1.md

5. Commit the changes.

git commit -m "put a descriptive message here"

6. Push your local changes to the remote repository.

git push

Exercise 2: Checkout

1. Checkout to the previous commit.

git checkout HEAD~

2. Look at the content of file_1.md. What do you see?
3. Check your current position in the tree of commits, indicated by (HEAD).

git log --all --decorate --oneline --graph

Note: Instead of typing the long git log command every time, you can create an alias for it (here git lg):

git config --global alias.lg "log --all --decorate --oneline --graph"

Exercise 3: Branch

1. Create a new branch from the commit of the previous exercise.

git branch new-branch

2. List all the branches.

git branch

3. Switch to the new branch.

git checkout new-branch

4. Make a change in file_2.md.
5. Commit your changes.
6. Look at the current tree of commits.

git log --all --decorate --oneline --graph

Note: The git branch new-branch and git checkout new-branch commands can be combined into a single command:

git checkout -b new-branch

Bonus step: Try to push new-branch to the remote repository (origin). Note that new-branch does not exist on the remote repository yet.

Exercise 4: Merge

1. Make sure that all changes are commited on new-branch. Running git status should show nothing to commit, working tree clean.
2. Switch back to the main branch.

git checkout main

3. Merge the changes from new-branch to main.

git merge new-branch

4. Look at the current tree of commits.

Bonus Exercise: Merge Conflict

1. Create a branch conflict-branch from main.
2. Make a change in file_1.md in conflict-branch and commit it.
3. Switch back to main and commit a different change in file_1.md that conflicts with the change commited in conflict-branch (e.g. change the same line).
4. Merge conflict-branch to main and resolve the conflict.

Exercise 5: Pull Request

1. Checkout to the main branch and push it to the remote repository.
2. Go to the GitHub page of your forked repository.
3. Create a pull request from your main branch to the original repository's main branch.
4. Add the description and comments to the pull request.

Additional Resources

• https://learngitbranching.js.org/ Git branching for beginners
• Exercises on rewritting history
• Do you really know git? Lightning talk from fellow EPFL RSE