04-basics.md

Git 4: Basics

Some Vocabulary

• Git - version control software
• Repository - a folder containing your files and also containing a structure that helps keep track of changes in those files. When you intialize a repository, git creates a hidden folder (.git folder) that stores the changes to those files.
• GitHub - a place to host git repositories and collaborate
• Local Repository - the version of a git repository on your local computer
• Remote Repository - the version of a git repository stored somewhere else that your local repository is connected to (frequently on GitHub)
• Commit - the basic unit of a git repository is a commit. It is a set of changes to a file. A commit usually comes with an id as well as a commit message that describes the change.

Within a Repository you have

• Untracked Changes - files that are in your folder but that git doesn't pay attention to.
• Staging Area - a place where you can put files before you commit them. Once files are in the staging area, git is paying attention to them.
• Commit Log (aka Git History) - all of the commits (previous changes) to all of the files in your repository.

Components of a Git Repository

1. The working directory

• git init creates a git repo inside current working directory

2. The staging area

• git add . adds changes from the working directory to the staging area
• git add <filename> adds changes to filenames specified from the working directory to the staging area

3. The commit

• git commit -m "commit message" adds changes in staging area to the repository
• git log shows

Protip: Run git status after each command in the beginning because it allows you to visualize what just happaned.

Github

• Your Github Page
• Social Features

Key Terms

• github - a service that hosts git remote repositories, and provides a web app to interact / collaborate on them
• remote - another repository that can be syncronized with a remote
• upstream - the name for a remote read-only repository
• origin - the name for a remote read-and-write repository
• clone - download an entire remote repository, to be used as a local repository
• fetch - downloading the set of changes (commits) from a remote repository
• pull - fetching changes and merging them into the current branch

Example: fruit-basket

1. Create 🍒🍎🍌🍇🍑🍉🍍 basket

   cd ~/Development/
   mkdir fruit-basket
   cd fruit-basket
   
   echo "i am cherry" > cherries.txt
   echo "i am a strawberry" > strawberries.txt
   echo "i am a watermelon" > watermelons.txt
   

2. Initialize repository

   git init
   
   git status
   git log
   

3. Add the fruits to the staging area.

   git add cherries.txt
   git add strawberries.txt
   git add watermelons.txt
   
   git status
   git log
   

4. Create a commit.

   git commit -m "add cherries, strawberries, and watermelons"
   
   git status
   git log
   

5. Create a blank github repo called "fruit-basket".

6. Set your remotes (follow the instructions in the new github repository, it should look something like below).

   git remote add origin [email protected]:XXXXX/XXXXX.git
   git push --set-upstream origin master
   

7. Push the commit.

   git push
   
   git status
   git log
   

Example: assignments

1. Backup the assignments directory.

2. cd into your directory ~/Development/assignments

3. run pwd and ls to remind yourself where you are and what is there

4. intitialize a git repository in the folder. Your shell prompt (PS1) should also show that we are now in a git repository.

   git init
   git status
   git log
   

5. Add day 1 homework to the staging area.

   git add sayhello.py
   git add expensive_water.csv
   git add expensive_water_summary.txt
   git add description.txt
   git add output.csv
   git add summary.txt
   git status
   git log
   

6. commit

   git commit -m "add day 1 homework"
   git status
   git log
   

7. create a blank github repo called "assignments"

8. set your remotes (follow the instructions in the new github repository, it should look something like below)

   git remote add origin [email protected]:<username>/<repo>.git
   git push --set-upstream origin master
   

9. push your commits

   git push
   

10. check if the code is pushed online

Example: universe

1. cd into your directory ~/Development/universe

2. run pwd and ls to remind yourself where you are and what is there

3. intitialize a git repository in the folder

   git init
   git status
   git log
   

4. add mars.txt

   git add solar_system/planets/mars.txt
   git status
   git log
   

5. commit

   git commit -m "add mars"
   git status
   git log
   

6. add earth

   git add solar_system/planets/earth
   git status
   git log
   

7. commit

   git commit -m "add earth"
   git status
   git log
   

8. create a blank github repo called "universe"

9. set your remotes (follow the instructions in the new github repository, it should look something like below)

   git remote add origin [email protected]:XXXXX/XXXXX.git
   git push --set-upstream origin master
   

10. push your 2 commits

    git push
    

11. check your repository online by refereshing the page in github

Try It

1. Add venus.txt and commit it with the message "add venus".
2. Add jupiter.txt and uranus.txt and commit it with the message "add jupiter and venus".
3. Add the rest of the planets folder and commit it with the message "add remaining planets".
4. Add the rest of the stars folder and commit it with the message "add stars".
5. Run git status to check for any more "untracked files". Add the remaining files and commit them.
6. Push these commits to github.

Example: cloning and pulling

1. Clone code4policy repository.

   git clone [email protected]:dmil/code4policy.git
   

2. Dhrumil will now push a commit.

3. Run git pull followed by git log to see the new commits.

Git vs Github

Git is a distributed version control system (VCS). Distributed means that there is no one central server that stores all of your code- you can have redundancies (copies) of the code wherever you like. There is always one copy of the code (along with its entire history) on your local computer. Other copies of your code are each referred to as "remotes". Github.com is a very popular remote used for Git projects such as it is almost synonymous with Git now. There are of course other alternatives such as BitBucket and GitLab.