Assgn 2b

Assgn 2b (individual): Git branching & merging

Instructor Instructions:

• For this assignment students submit directly on Github repo. Instructor needs to have this repo available for the students and to replace our repo link at Step 4 of the previous exercise (Assgn 2a).
• Suggested time: 7 days

Posting for Students:

Practice assignment for Git+Bash

Git Practice #2: Checkout and branch

Note: Always prefer the official Git documentation and its reference manual to learn about the git commands rather than following random, outdated, and misleading tutorials from the web. If you don’t remember syntax of a specific git command, try the --help option (e.g., git commit --help). Two exceptions I will recommend are the simple git guide and Learn Git Branching - a testing environment for you to play around branches.

Part I: Parallel universes

This exercise will make changes in one file in two parallel branches.

1. Go back to your clone of bash_basics on your computer.
2. Pick any one of the numbered Bash scripts. Run it using sh "name of script" in your Git Bash to see what it does, and then do the exercise described in the comment section at its end by adding new commands to the file. You can look inside the basics.sh file to get some hints, or use the Conquering the Command Line book.
3. Add and commit your edited file, and push back to your own Github fork like last time (Note: If you’re committing to a new branch name, make sure to git push --set-upstream origin "name", like we did in the previous assignment).
4. Now, we will look into the history to see a suitable place to travel back in time before our last commit. Use the git log command (or the commit lists in the UIs) to find the ID# of your first commit from last assignment. Press “q” to quit from the git log command.
5. The actual time travel is achieved by using the git checkout "ID#"command, using the “ID#” from the previous step, which will transform your code back to that commit. Do git log again to confirm that it shows on the top of the list. The point of this is to go back to that time, but we will not do anything with the file you created last time.
6. To create the parallel universe, create a new branch git branch "name" and then switch to that branch with git checkout "name" (OR you can do the two in one step with git checkout -b "name"). Notice the dual use for the git checkout command.
7. Re-do steps 2-3, which will be happening on the new branch, that is in the parallel universe. Make sure you pick and edit the same file and around the same lines in it, but this time do it slightly differently. This will result in having changes to the same file in two parallel branches of the repository.
8. Now you should have two branches: master, and the new one you created. Look on Github under Insights->Network to study your branches and the different commits in each (alternatively, view them locally using the git log --graph --all command). Take a screenshot of your “two-branches” graph and add this file into your repository. Don’t forget to add/commit/push.
9. Congratulations, now you can move onto part II.

Part II: U.N. conflict resolution

We will now reconcile the two separate parallel universes into one.

1. On your local copy, make sure you’re on the master branch (use git status to check and git checkout "branch name" to switch between branches). Then, run git merge "branch_name" to merge the changes from your new branch into the master branch. You will get a conflict, OMG!
2. Use git status to get a recommendation from git. When in trouble, always ask for status.
3. Do not proceed to commit without resolving the conflict! Open the file you edited and observe how git changed it. It should have added marks «< === »> to indicate parts changed in the two branches.
4. Pick the parts you like to keep, and delete the rest and the marks added by git. Make sure your script still works.
5. Add and commit to mark the conflict resolved. Consult git status to confirm. Push to set it in stone.
6. Look on Github under Graph->Network again to see how your branches were merged together. There should be an arrow that merges them into a single branch. Take a screenshot of your “after-merging” graph and add this file into your repository also. Don’t forget to add/commit/push.
7. Create a Pull Request against my repository to submit, like in the previous assignment. If you already have an outstanding pull request, your commits will just show up in there. So you don’t need to create a new one.