CPEN 221 / Fall 2020 / Lab 4A

Git Branching and Merging

One important aspect of using a source code control system is to manage simultaneous updates to the code base and to merge the changes. To familiarize yourselves with this aspect of git, read A Hacker’s Guide to Git.

Resolving Conflicts

To understand how one can resolve conflicts, follow these steps. This task is set up so that one person can complete all the steps (including creating the conflict) although conflicts are more common when multiple people are contributing to a project. This is not the only way to resolve a conflict but it is intended to be a start.

• Clone your assigned Github repository: git clone <https://github.com/CPEN-221-2020/><your-repo> lab4a which will clone the repo in a local directory lab4a.
• Change to the lab4a directory and create a new branch b1 and switch to it: git branch b1 followed by git checkout b1
• Add an empty file named README.txt in the lab4a directory and push to Github:

git add README.txt
git commit -m "Added README"
git push origin b1

• Now, from the parent directory for lab4a, clone branch b1 of your repository using the command: git clone -b b1 <https://github.com/CPEN-221-2020/><your-repo> lab4a1 which will clone the repo in a local directory lab4a1. (This would allow the two cloned repositories to be on the same machine, if necessary.)
• In the lab4a1 directory, add the following line to README.txt: Hello from Lab4a1. Then commit and push the change to Github.
• In the lab4a directory, add the following line to README.txt: Hello from Lab4a. Commit this change and execute a pull: git pull
• Git will indicate that there is a merge conflict.
• Edit README.txt in lab4a to have the two lines in the correct order (Lab4a before Lab4a1). You will remove the conflict indicators placed by Git.
• Add, commit and push README.txt from lab4a1.

Merging Branches

• In lab4a, switch to the master branch:

  git checkout master

• You should not see README.txt in your directory for now.

• Now add any new file to this directory, then add, and commit this file to the repository.

• Now, merge the master branch with the b1 branch:

git merge b1

• At this point you should see README.txt and the new file that you added. The two branches have been merged and you can keep working on the master branch.