Homework 1, due 08.00, 26/1-2018

Version control and Git

1. Sign up for a free personal account and apply for the student development pack (allowing you to have private repositories) at the student development pack.
2. Set up Git on your machine if you haven’t already. There are good instructions on the official git-scm.com.
3. Create a private Git repository named homework1-last-name. To do this click start a project or simply navigate to github.com/new. Select the button Initialize this repository with a README.
4. Now you will clone the repository you just created. Go to the root of your home directory (i.e. type cd) and create a directory where you keep all the repositories, e.g. mkdir repos and change into that directory (cd repos.)
5. Next point your browser to your repository and click the green button that says clone or download. Clicking this button gives the adress to the repo. Copy the text and paste it into your terminal window (something like git clone https://github.com/appelo/APPM-4720-5720-S18.git) and hit enter. You should now have a directory with the name of your repository, change into that directory.
6. In the directory your_repo there is a file called README.md. The extension .md indicates that this file is written in Markdown. For the repository above it looks something like this:

# APPM-4720-5720-S18
Course content for APPM 4720 / 5720 Spring 2018

7. Open the readme file using emacs or vi and make some changes to the file, for example you can add a nice poem. If you haven’t used emacs or vi before it may be a bit easier to get started with emacs.
8. Once you are done editing your readme file you will first add it to your local git repository, commit locally and then push your changes to your remote repository.
   • git add README.md
   • git commit -m "Updated the README file"
   • git push
9. Go through this tutorial to see the basic work flow of git.
10. Now create a file from the terminal touch seriefigurer.txt and add the following comic characters to the file:

Kalle Anka
Musse Pigg
Pomperipossa
Bamse
Skalman
Nalle-Maja

11. Add and commit the file and then add some more of your favourite comic characters (they don’t have to be in Swedish). Add and commit your changes.

12. Now you realize that, strictly speaking, Pomperipossa is not a comic character but rather a fictional persona (a witch to be precise) and you need to correct this. Rather than changing the master branch you should checkout a new branch that we call pom-fix from an earlier snapshot of the history. To do this we inspect the logfile for the repository by git log which outputs something like this:

    commit f2a2971ff715ae801f84dd93c5626c010e46404b
    Author: Daniel Appelo <daniel.appelo@colorado.edu>
    Date:   Tue Jan 16 13:43:52 2018 -0700
    
    Commit one - helpful text goes here
    
    commit 12d3ece48d33711b32c6af8c61ceac31bab422a4
    Author: Daniel Appelo <daniel.appelo@colorado.edu>
    Date:   Tue Jan 16 13:41:08 2018 -0700
    
    Initial commit
    

    Now, suppose we want to go back to the second commit, then the important number is the commit SH1 string f2a2971ff7… If we do git checkout f2a2971ff7 -b pom-fix then in one stroke we create a branch called pom-fix which is an identical copy of the master branch at the time of the commit f2a2971ff7…. To see what branches you have you can say git branch.

13. Replace Pomperipossa with Gargamel and add and commit in your changes. To merge your branches checkout your master branch again and say git merge pom-fix. Since there is no conflicts in the two files the merge should go through automatically. If it did you can delete the branch by git branch -d pom-fix.

14. Sometimes things don’t go quite this smoothly. Again do git checkout 12d3ece -b pom-fix but this time change Pomperipossa and also add a name at the end of the list. Add and commit the changes and checkout the master branch and try to merge. Now you will get an error message that looks something like this:

    Auto-merging seriefigurer.txt
    CONFLICT (content): Merge conflict in seriefigurer.txt
    Automatic merge failed; fix conflicts and then commit the result.
    

    A git status . will tell you what files have conflicts. Open the file with a conflict and fix it by keeping all the names (note that Pomperipossa did not cause a conflict). Another git status . will tell you that your merge conflict is resolved but that you still have to do a commit (first add). Do so and push the changes to github. Once you have pushed the repository you can go to the insights page for the repository and look at the network to see a graphical representation of the process.

15. To conclude the first homework add your group members as collaborators on the gighub page for your repository and also add me.

16. To hand in your repository send me an e-mail with the subject line APPM 5720 and a link to the homepage of the repository.