Added git diff and git cherry

Signed-off-by: Nastasie Raul-Ionut <ion_nastasie@yahoo.com>

Author: misespuneraul

README.md

@@ -170,14 +170,13 @@ For that, in the GitHub web interface for the pull request follow the steps:
    ./gh-reset-repo.sh
    ```
 
-
 1. Create your own commits and pull requests.
    Be creative.
 
    Create at least one pull request with two commits.
    Use the `Squash and merge` merge strategy.
 
-## Understand `git merge` and `git rebase`
+## Understanding `git merge` and `git rebase`
 
 When working with multiple branches, we often need to bring changes from one branch into another.
 The two most common ways to do this are:
@@ -487,7 +486,6 @@ They may contain the same changes, but they are rewritten commits.
 * the result looks like the work happened in a straight line
 * there is usually no merge commit
 
-
 ### Now you want to remove all the commits created during this rebase exercise.
 
 After the rebase, the commits created during this exercise are still on `<your-rebase-branch-name>`, but they were rewritten on top of `main`.
@@ -527,6 +525,53 @@ If needed, delete `<your-rebase-branch-name>` as well:
    git branch -D <your-rebase-branch-name>
    ```
 
+## Checking your work with `git cherry` and `git diff`:
+
+Let's take a quick look at two very useful commands for checking your work: `git diff` and `git cherry`.
+
+First, make sure you're on the `main` branch. Use either `git status` or `git branch`. Now, let's create a new branch:
+``` console
+git checkout -b <branch-name>
+```
+
+## `git diff` is used to see the changes you've made and what state they're in.
+
+Go to `cpp-hello/hello.cpp` and change the message it prints. Now run 
+``` console
+git diff
+```
+and you should see the change you've just made. `git diff` with no arguments will show you your unstaged changes (as in: changes you haven't comitted yet).
+
+To see the changes you've commited but haven't pushed, use:
+``` console
+git diff --staged
+```
+It shouldn't show anything for now. Commit your change to `cpp-hello/hello.cpp` and run it again.
+
+Then run `git diff`. Since your changes are now staged, it won't show anything.
+
+The last use of `git diff` is to show the difference between branches. Using:
+``` console
+git diff main
+```
+will show the difference between your current work and the `main` branch. `git diff --staged main` also works.
+
+## `git cherry` shows the difference in commits between two branches.
+
+Try running:
+``` console
+git cherry main
+```
+You should see a hash that looks familiar. If it doesn't, try running `git diff main` again. Spoiler: it's the same commit (or at least it should be if you've done everything correctly).
+
+`git cherry <second-branch>` shows you commits that your current branch has but `<second-branch>` doesn't have.
+
+Remembering and recognizing hashes is hard though. Try running:
+``` console
+git cherry -v main
+```
+This way, you can also see the commit message of the commits missing from `main`.
+
 ## Configure Merge Strategy
 
 We want to configure Rebase and merge as the only merge strategy.