class: center, middle, inverse, title-slide # Merge conflicts <br> ⛔ ### Dr. Çetinkaya-Rundel --- layout: true <div class="my-footer"> <span> Dr. Mine Çetinkaya-Rundel - <a href="http://www2.stat.duke.edu/courses/Fall18/sta112.01/schedule" target="_blank">stat.duke.edu/courses/Fall18/sta112.01 </a> </span> </div> --- class: center, middle # What is a merge conflict? --- ## Merge conflicts When two collaborators make changes to a file and push the file to their repo, git merges these two files. <img src="img/merge-no-conflict.png" width="400" style="display: block; margin: auto;" /> -- If these two files have conflicting content on the same line, git will produce a **merge conflict**. <img src="img/merge-conflict.png" width="400" style="display: block; margin: auto;" /> --- ## Resolving merge conflicts - Merge conflicts need to be resolved manually, as they require a human intervention <img src="img/merge-conflict-identifiers.png" width="800" style="display: block; margin: auto;" /> - To resolve the merge conflict - decide if you want to keep only your text or the text on GitHub or incorporate changes from both texts - delete the conflict markers `<<<<<<<`, `=======`, `>>>>>>>` and make the changes you want in the final merge --- class: center, middle # Application exercise --- ## <i class="fas fa-laptop"></i> AE 06 - Merge conflics - Clone your assignment repo in RStudio Cloud (`ae-06-merge-conflicts-TEAMNAME`), and open the R Markdown file. - Assign the numbers 1, 2, 3, and 4 to each of the team members. - Take turns in completing the exercise, only one member at a time: .midi[ - Member 1: Change the team name to your team name, knit, commit, push. - Member 2: Change the team name to something else, knit, commit, push. You will get an error. Pull. Review the document with the merge conflict. Resolve the conflict with the preferred change. Commit and push. - Member 3: Create a plot displaying the relationship between `price` and `carat`, controlling for `cut` of the diamonds (see next slide for the plot). Knit, commit, push. You will get an error, read it, and pull. No merge conflicts should occur. Now push. - Member 4: Set the `alpha` level to `0.5`. Knit, commit, push. You will get an error. Pull. Review the document with the merge conflict. Clear the merge conflict by choosing the correct/preferred change. Commit, and push. - All members: Pull, and observe the changes in your document. ] --- class: middle Plot for Member 3 to recreate (the others can help of course!): - data: `diamonds` - variables: `carat`, `price`, `cut` <!-- --> --- class: center, middle # Review --- .question[ What does the following message mean? ] <br> <img src="img/merge-conflict-error.png" width="800" style="display: block; margin: auto;" /> --- .question[ What does the following message mean? ] <br> <img src="img/merge-failed.png" width="800" style="display: block; margin: auto;" /> --- .question[ What does the following message mean? ] <br> <img src="img/no-merge-conflict.png" width="800" style="display: block; margin: auto;" /> --- .question[ What does the following message mean? ] <br> <img src="img/merge-made.png" width="800" style="display: block; margin: auto;" /> --- ## Tips for collaborating via GitHub - Always pull first before you start working. - Commit, and push, often to minimize merge conflicts and/or to make merge conflicts easier to resolve. - If you find yourself in a situation that is difficult to resolve, ask questions asap, don't let it linger and get bigger.