Break it

1 Explore commit history

You might not find yourself needing to look back through your commit history often, but it is useful to have some familiarity. For example, I recently used it to recover a chunk of code to make a figure I deleted a month ago and decided I actually wanted.

Navigate to the workshop website’s GitHub repo. Using GitHub’s commit history feature, find the commit message “Reworked to add auto merge and conflict examples” and find the answers to the following questions.

  1. What is the commit ID?

Commit ID: 7ae9d4e.

  1. How many files did I edit?

Only one file (collab_act.qmd)

  1. What change did I make to line 55 in the older version?

I only made one small change where I corrected the capitalization of “GitHub.” Admittedly, that is not a very exciting change.

2 Break everything (and fix it)

2.1 Break your code

Using the IntroToGit_Activity repository you forked in the collaboration activity, edit the script.R file by replacing the code to create the plot with the code below.

plot <- ggplot(iris, aes(x = Sepal.Length, y = Sepal,Width, color = Species)) +
  geom_point(size = 2) +
  geom_smooth() +
  xlab("Sepal Length (mm)") +
  ylab("Sepal Width (mm)") 
  scale_color_manual(values = c("tan", "wheat", "burlywood2")) +
  theme_bw()

  1. Try running the new code. Does it work? Take a second to try to identify the source(s) of the error without using the diff.

  2. View the diff for the script.R file. Can you tell where the changes to the code occurred?

There appear to be changes in three lines, with the change in the line 16 resulting from a change in line 15.

RStudio doesn’t do quite as good of a job at highlighting the exact places where changes occurred as Git, but it will help you narrow it down. If you look closely at line 11, the period in Sepal.Width was changed to a comma and in line 15 the + at the end of the line was removed.

  1. Fix the code by reverting the change using the RStudio GUI and check to see if the code runs as expected.

In using the GUI, open the diff window and click revert.

  1. (More advanced) - How would you recover the previous version if you committed the change but haven’t pushed it to GitHub yet?

    • Edit the code, save the file, and commit the changes but don’t push.

    • Use the terminal to perform a “soft” reset of your last commit

In the terminal run $ git reset --soft HEAD~1. This will reset your local repo to right before you hit commit. Since we used a soft reset, it will keep all of your files and edits as they were. This can be particularly useful when you accidentally push too large of a file.

2.2 Break your repo

xkcd

Create a more realistic repo:

  1. Create a new document in the forked repository (or another repository that isn’t important to you).
  2. Add this file to .gitignore so that it won’t be pushed to GitHub. Imagine that this is a large data set.
  3. Sync your local repo with GitHub with usual the pull->stage->commit->push workflow.

Now assume that you are experiencing an error that cannot be resolved with one of the other methods. Reset your repository by following the xkcd steps.

  1. Copy the forked repository to another location on your computer
  2. Delete the original folder
  3. Clone the repository again from GitHub
  4. Check to see if any documents (e.g. the one you created early are missing)
  5. Move any missing documents into your new repo.
  6. Make sure you can pull and push changes.