Beginning to add a page for the commit section exercises

Author: bbrydsoe

docs/commits-exercises.md

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+# 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
+
+!!! note 
+
+    The goal of this exercise is to learn to use the `git log` command. 
+
+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?
+
+!!! hint "Hints for this exercise"
+
+    - oneline
+    - graph
+    - reflog
+
+## 2. Recovering the HEAD 
+
+!!! note 
+
+    The goal of this exercise is to learn to identify a "detached HEAD" situation and recover from it. 
+
+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`
+
+!!! tip "Hints for this exercise"
+
+    - git checkout <ref>
+    - rev-parse
+    - cat .git/something
+