Extend section on remotes

1. Introduce the concepts of decentralized version control
2. Add short intro on Github/GitLab

Cou-authored-by: Georgiana Mania <mania@dkrz.de>

lectures/git/slides.qmd

@@ -314,8 +314,13 @@ Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
 
 Example from [kernel.org](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=90ca6956d3834db4060f87700e2fcbb699c4e4fd)
 
+# Decentralized version control
 
-# Remotes {auto-animate=true}
+* Git is a **de**centralized version control system
+* Each repository contains the full project history
+* _Technically_ there is no single point of truth^[_Practically_ teams agree on one main repo]
+
+## Remotes {auto-animate=true}
 
 * Adding a remote repository
   ```bash
@@ -334,7 +339,7 @@ Example from [kernel.org](https://git.kernel.org/pub/scm/linux/kernel/git/torval
   git pull origin <YOUR_BRANCH>
   ```
 
-# Remotes {auto-animate=true visibility="uncounted"}
+## Remotes {auto-animate=true visibility="uncounted"}
 
 * Adding a remote repository
   ```bash
@@ -353,7 +358,19 @@ Example from [kernel.org](https://git.kernel.org/pub/scm/linux/kernel/git/torval
   git pull
   ```
 
-## Merge request on GitLab DKRZ
+## Github and GitLab
+
+* There are many services to host git repositories
+* They offer plenty of additional functionality (merge/pull requests, code review, automated testing, ...)
+* Github offers by far the largest user base, while GitLab (as opens-source solution) is often self-hosted
+
+:::fragment
+
+We are using **GitLab** for this lecture! 
+
+:::
+
+## Merge request on DKRZ GitLab 
 
 ![](static/mr.png)