Exercises - Traversing the commit tree¶

In order to do these exercises, you need to download the exercises zip file. You can do that either by cloning the repository or by just getting the zip file with wget.

• Do ONE of the following:
  • git clone
    1. git clone https://github.com/hpc2n/course-intro-git.git
    2. cd course-intro-git
    3. unzip git_materials.zip
    4. cd git_materials
    5. cd 4.commits
  • Fetch with wget
    1. wget https://github.com/hpc2n/course-intro-git/raw/refs/heads/main/git_materials.zip
    2. unzip git_materials.zip
    3. cd git_materials
    4. cd 4.commits

You are now in a directory with 7 subdirectories, one for each exercise.

1. Investigating the commit history¶

Found under git_materials/4.commits/1.log there is a directory named repository. Enter it and perform the following steps:

1. Investigate the history. How many commit does the main branch contain?
2. Can you make the output of the command cleaner?
3. Are there any other branches? How many? What are they called?
4. Try to filter the output so that only commits that contain the word “abandon” in the commit message are shown.
5. Does the reference log contain anything interesting? Can you see where the HEAD was 6 steps ago?

2. Recovering the HEAD¶

Enter the repository/ directory under git_materials/4.commits/2.recover_head and perform the following steps:

1. Enter the repository/ directory and check whether the HEAD is detached.
2. If the HEAD is detached, return the HEAD back to the tip of the branch.
3. Confirm that that the HEAD indeed points to the tip of the branch`

3. Stashing uncommitted changes¶

Enter the repository/ directory under git_materials/4.commits/3.stash and perform the following steps:

1. Identify the first commit (This is going to be a cake recipe).
2. Try to checkout the commit in order to identify the initial title of the recipe. If necessary, stash the changes. What was the initial title of the recipe?
3. Restore the HEAD and pop the changes from the stash.
4. Confirm that the changes were applied correctly and that the stash is empty.

4. Discarding the latest commit¶

Enter the repository/ directory under git_materials/4.commits/4.discard and perform the following steps:

1. Discard the latest commit. Also discard the changes in the working tree.
2. Confirm that the commit is no longer reachable from master. Confirm that the recipe.txt no longer contains the section “Other ideas and hints”.
3. Try to restore the discarded commit. (optional)

5. Amending previous commit¶

Enter the repository/ directory under git_materials/4.commits/5.amend` and perform the following steps:

1. The ingredient list in the repository/recipe.txt file is missing an ingredient. Add two eggs to the ingredient list.
2. Stage the changes and amend the previous commit (Add remaining ingredients and directions).
3. Validate the operation. The log (git log) should contain three commits and the most recent commit (Add remaining ingredients and directions) should contain the new added ingredient (git show <commit>).

6. Revert the latest commit¶

Enter the repository/ directory under git_materials/4.commits/6.revert and perform the following steps:

1. Revert the latest commit.
2. Confirm that the commit tree indeed contains the revert commit. Confirm that the recipe.txt file no longer contains the section “Other ideas and hints”.

7. Proper commit workflow¶

Enter the repository/ directory git_materials/4.commits/7.workflow and perform the following steps:

1. You can confirm (git diff HEAD) that the repository/recipe.txt file contains uncommitted changes. That is, the recipe have been converted to metric system.
2. You can also confirm (git diff --cached) that some of these changes have been already staged.
   
   As you can probably guess, the first commit we are creating is going to convert the measurements to metric.
   The changes that are related to the pan size and the oven temperature (8th step the the directions) are going to be committed separately.
   
3. Store the the unstaged changes to the stash:

$ git stash --keep-index

The --keep-index options tells Git to keep the staged changes. Otherwise Git would stash them.
4. Now, investigate the content of the repository/recipe.txt file. You can see that the 7th step in the directions contains an unconverted measurement. This means that whoever created this exercise forgot to stage this line. This would correspond to a situation where the source code does not compile or does not function correctly.
5. Pop the unstaged changes from the stash:

$ git stash pop

Verify the repository/recipe.txt file.
7. Commit changes.
8. Pop the unstaged changes, and stage and commit changes that are related to the pan size and the oven temperature.

This is going to be the second commit.

Confirm that the two commits you created indeed contain the desired changes.