Collaborating on GitHub

• Authors: Serena Jeblee
• Research field: Computational Linguistics
• Lesson topic: Collaborating on GitHub
• Lesson content URL: https://github.com/UofTCoders/studyGroup/tree/gh-pages/lessons/git/collaboration
• Lesson video stream: https://www.youtube.com/watch?v=vrftiQcqIYM

Overview

• A brief review of basic git usage
• Some helpful git commands
• Help! I’ve made a mistake! (aka how to unstage changes and undo commits)
• Merge conflicts
• Branches
• Forking and Pull Requests

If we have time:

• Stashing changes
• Rebasing

Whirlwind Overview of GitHub

• What is GitHub?
• What is version control?
  • version control helps you collaborate on code especially when your changes might overlap
  • master repo vs local repos
  • master - shared version stored on GitHub or a server
  • local - your local copy that you can play with and make changes to, only seen by you until you push your changes
• How to contribute code

  git clone [repo-url]
  git pull # syncs latest version from the master repo to your local repo
  [edit the code]
  git add [file] # stages code for commit (git remove does not unstage, it stages a deletion, we'll get to unstaging in a bit)
  git commit # create a record of the changes you've made
  git push # sync your local changes to the master repo
  

• Fork and pull request if you can’t push directly
• Some rules for good commits
  • commit should represent one change or a small set of related changes (like a bug fix or new feature)
  • all committed code should be functional and tested
  • make sure the commit message is descriptive

Get Started

• Create helloworld.sh

  echo "Fancy code will go here"
  echo "More fancy code"
  

• Run it and commit it

Help! I messed up and now nothing works!

• Add junk code to hello.sh and run it
• Undo the changes to a file

  git checkout -- [file]
  

• Unstage the changes, but keep them

  git reset --soft HEAD
  

• Undo the changes and go back x commits

  git reset --hard HEAD~x
  

Oops, I didn’t mean to commit that

• Add the junk code back and commit it
• Undo a local commit

  git reset --soft HEAD~1 # keeps changes, but undoes the commit
  

• Pushed commits - do a revert commit

  git revert [commit-hash]
  

The Dreaded Merge Conflict

• Clone a new copy of your repo
• Change a line and commit it
• Go back to your original repo
• Change same line to “My version is better!”
• Commit it

  git commit
  git pull
  

• Resolve the merge conflict, delete »> «< lines, add and commit

Branches

• Branches allow you to have different commit histories in the same repo
• Useful for feature work
• For more info see: https://github.com/UofTCoders/studyGroup/blob/gh-pages/lessons/git/branches/lesson.md

Forking and Pull Requests

• Used when you don’t have direct push access to a repo
• Fork: creates your own version of the repo that you can commit to
• When you’re finished committing all of your changes, create a pull request
• Pull Request: tells the main repo that you have some commits you would like to merge, and allows others to review them first

Reviewing Code

• Look for:
  • errors (typos, potential infinite loops, concurrency issues, etc)
  • overly complicated code
  • unclear variable names
  • missing comments or documentation
• Provide constructive suggestions for how to fix it

Updating the Pull Request

• Try to address all comments, if you’re not going to change something, say why not
• Make a new commit and push it to the branch your pull request is on

Merging the Pull Request

• Requires push access to the repo
• If there are conflicts, you’ll have to check out the pull request and resolve them, otherwise you can merge online
• For more info on how to merge a pull request, see https://help.github.com/articles/merging-a-pull-request/