Basic Git Workflow

Overview

Questions

• How can I make updates and save it into the version control?
• How can I work on my 'copy' of the repo and merge it back?

Objectives

• Learn the basic Git workflow: update-add-commit
• Implement branches

In this section, you will learn how to work on your local repo

The basic workflow

The basic Git workflow ¹ goes something like this (see the figure below):

1. You checkout the project and modify files (in your working directory)
2. You stage the changes you want to be part of your next commit
3. You make a commit to the repo, which takes the files as they are in the staging area and stores that snapshot permanently to your Git directory.

The Three Git Areas (States)

The files that are tracked for changes by Git can exist in three states:

• modified: files that you updated or added
• staged: files that are ready and that are marked to go into your next snapshot (to be committed/saved)
• committed: data that is saved to your local repository

Depending on their state, the files move between three areas in your local directory²:

• You modify the files in the Working Directory (also known as Working Tree). Working directory is the visible section of your repo.
• Files that are ready to committed are moved to Index/Staging Area. This action is commonly refered to as staging (think of it as getting the files ready for the snapshot).
• The local Git repository holds the files you commit from Staging Area

Get your files ready for the snapshot	Store them permanently in the repo

Git branches

A repository can have one or more branches. The main branch, where all changes are eventually merged into, is called master. Developers use branches to explore and experiment with updates/features and merge their updates into the master when they are ready. (In the figure, commits P, Q, and R are on a branch. Commit P on the branch was created from the master. The branch is then merged into the master when ready)

Getting an Intuition

Try the following git commands one at a time on http://git-school.github.io/visualizing-git/ (This page is embedded below if you prefer to stay on this page. Trying refreshing if you see a blank embedded window)

git commit -m "Femur Mesh"
git commit -m "TIbia Mesh"

# Make a new branch from "Femur Mesh" commit to add material properties. Give commit id for "Femur Mesh"
git branch  <branch name> <commit id>
git checkout <branch name>
git commit -m "Femur Properties"
git merge master
git checkout master

Few things to note from the illustration

• Each commit is identified with a unique commit hash.
• A branch is created to work in parallel. The branch is then merged into the master branch.
• the HEAD moved as you switched between the branches. HEAD indicates the branch where the next commit will be written on. (Think of it like the 'recording head' that writes on a gramophone record or CD/DVD)

Exercise: Commits and Branches

As an exercise, we will be collaboratively creating a list of the workshop participants

1. Clone the exercise repo

Go to the location where you would like to clone the exercise repo https://virtual.openvt.eu/viva-workshops/workshop-exercise. Use the git clone command. Use the address for SSH cloning. (On Windows, an easy option is to open the Git Bash using right click in your preferred directory)

```
git clone git@virtual.openvt.eu:viva-workshops/workshop-exercise.git
```

Enter the repo and check the files in the repo

cd intro-exercise

You will be able to see a README.md and the hidden .git folder

2. Make a branch and switch to the new branch

Create a branch FirstName for this exercise.

git checkout -b FirstName

git checkout -b <branch-name> is shorthand for:

git branch <branch-name>
git checkout <branch-name>

3. Make changes to the repo

In this step, add your name to the README file in your branch and stage the updates to Index(Staging Area) for committing them.

Open the README.md file in any text editor and add your name to the Participants section. Save the changes.

4. Check the status of your repo

Check the status of your repo

git status

You can see the changes to the repo

5. Stage your updates

The first step to save your updates is to stage it (to move it to the Index/Staging Area). git add is the command for this action

git add README.md

6. Commit your changes

Now you are ready to make the commit(save) to your Git repository (Doing git status again will shown that the staged files are staged(or are currently in the index region))

You need to provide a commit message as you make the commit. The easy way to do this is to give a one line commit message with the git commit command

git commit -m "Add <your-name> to README.md"

If you again do git status now, you will see that the working tree is clean and everything has been committed

---

1. Text and figure adapted from https://git-scm.com/book/en/v2/Getting-Started-What-is-Git%3F ↩

2. 1.3 Getting Started - What is Git?, Pro Git Book, https://git-scm.com/book/en/v2/Getting-Started-What-is-Git%3F ↩