Learning Git

Installing git

• Instructions for installing on all platforms (Linux, Mac, Windows) are available here:
  https://git-scm.com/book/en/v2/Getting-Started-Installing-Git
• You can verify that your installation worked by checking the version of Git from the command line.
  • Mac Users: Open up your terminal
  • Windows Users: Open up Git Bash
  • Run the following command:

git --version

Generating Your SSH Key

• Check for existing keys
  
  ls -al ~/.ssh
• If you don’t have keys, then generate a key
  
  ssh-keygen -t rsa -b 4096 -C “YourEmail@mail.com”
• Start the key agent
  
  eval “$(ssh-agent -s)”
• Add the key to the agent
  
  ssh-add ~/.ssh/id_rsa

Copy Public Half of SSH Key to GitHub

• Log into GitHub -> Settings -> SSH and GPG keys
• Copy the key to clipboard and Paste
  • Mac Users
    
    pbcopy < ~/.ssh/id_rsa.pub
  • Windows Users
    
    cat ~/.ssh/id_rsa.pub > /dev/clipboard

Create your own repo on Github

• Click on button to create new repository  
• Repositories are a folder
  Create a folder with same name as new repo
  mkdir ~/members
  cd members
• Copy/Paste the GitHub commands
  echo “# test” >> README.md
  git init
  git add README.md
  git commit -m “first commit”
  git remote add origin git@github.com:{UserName}/members.git
  git push -u origin master
  

Create your own repo on Github (cont.)

• The first command initializes the repository
  
  git init
• The second command tells git to track an individual file
  
  git add README.md
• This commits changes on a tracked file
  
  git commit -m “first commit”
• Now we tell git where our remote repository is
  
  git remote add {name} git@github.com:{UserName}/members.git
• Save your local commited changes to the remote repository
  
  git push -u {name} {branch name}

Making a Commit (Adding to README)

• Add your Name to the README file as a bullet

• Save your changes
• “Stage” all files, commit, then push to GitHub
  git add .
  git commit -m “Update README” -m “Add Change”
  git push origin master
  

Clone a Repo

• Navigate to where you want repo to be
  
  mkdir ~/my-repos
  cd ~/my-repos
• Copy/Paste the GitHub commands
  git clone git@github.com:NorfolkDataSci/members.git
  
• Check that a folder with same name as the repo was created in the current working directory

Fixing a Merge Conflict

• When 2 people change the same lines of code it creates a “merge conflict”
• Merge conflicts need to be “resolved”, meaning reconcile the differences between commits
• The first sign is not being able to push your recent commits

Fixing a Merge Conflict (cont.)

• So you follow the hint and pull
  git pull
• Then you receive a message about a “CONFLICT”
  (fix conflicts, then commit)

Fixing a Merge Conflict (cont.)

• Open up the conflicted file (in this case README.md)

• You will notice weird markings
  • The marker showing the start of the conflict
    “<<<<<<< HEAD"
  • The marker showing the end of your change (HEAD)
    ”=======“
  • The marker showing the end of the server’s version
    ”>>>>>>> 7bd926b……“

Fixing a Merge Conflict (cont.)

• Open up the conflicted file (in this case README.md)
• Edit file to how you want it. Make sure to remove weird markings

• Commit like any other change and you’re done (Resolved!)
  git add .
  git commit -m “Fix merge conflict”
  git push
  

Fixing or Resetting Work

• It’s possible to erase commits back to a certain point
• Click on the commits button to view  
• Click copy button to get commit hash on clipboard

• Run the following command to reset your local commit history
  git reset ––hard 2feeb51899f80a2ddea5b353260841350285406f
• Commit like any other change, but add “-f” on your git push
  git push -f

Working on Branches + a Pull Request

• Start work on a “branch”. It’s a copy of your current state
  git checkout -b my_branch
• This branch is only local, so push it to GitHub
  git push -u origin my_branch
• Make a change to the README.md file, commit, & push
• Next switch back to master branch and look at README.md
git checkout master
• Your change is gone! It only exists on “my_branch”. Switch back now
git checkout my_branch

Branching + Pull Request

• Branches isolate code until ready to be “merged”
  Create a pull request when you are ready to merge
  • Look in GitHub for “my_branch”
  • Click the button that says “Compare & pull request”
  
• Pick a “target” branch (where you want new code to be applied)
• Review that your changes make sense
• Add a message outlining why this pull request is needed and how it essentially solves the problem of why it was needed