Restructuring of branches sections

* Add mermaid graphs to illustrate different branching schemes
* Move rebasing to backup slides
* Make the conflict example more verbose

lectures/git/slides.qmd

@@ -52,103 +52,188 @@ git config --global user.name "Your Name"
 git config --global user.email "youremail@yourdomain.com"
 ```
 
-## Hands-on Session! {background-color=var(--dark-bg-color)}
+## Hands-on Ssssion {background-color=var(--dark-bg-color)}
 
 1. Configure the username and email adress in your local git client
 2. Initialize an empty Git repository
 3. Create a file and add it to the repo
 3. Change the file, inspect the differences, and commit the changes
 
-# Branches 
+:::info
+On Levante: `module load git`
+:::
+
+# Branches
 
 ::: {.incremental}
 * Are versions of the code identified with a name (besides the existing hash)
-* Are used to encapsulate the changes required for a feature/bugfix 
+* Are used to encapsulate the changes required for a feature/bugfix
 * Allow incremental development without impacting the other branches
 :::
 
 
-## Branch operations 
-
- 
-```bash
-git branch b1     # create branch
-
-git checkout b1   # switch to the new branch
+## Create a branch
 
-git branch -m b2  # rename a branch
+Create a branch `develop` to work on a feature
 
-git branch        # check branches
+```bash
+git branch develop
+git switch develop
+```
 
-git diff b1..b2   # compare branches
+```{mermaid}
+gitGraph
+   commit
+   commit
+   branch develop
+   checkout develop
+   commit
+   commit
+```
 
-git branch -d b1  # delete branch 
+::: {.fragment fragment-index=0}
+Show differences between two branches
+```bash
+git diff develop..main
 ```
+:::
 
-## Merge a branch 
+## Merge a branch
 
-TODO add drawing !
+Merge the commits of `develop` into `main`
 
-```bash 
-git checkout master
-git merge b1 # merge branch b1 into master
+```bash
+git checkout main
+git merge develop
 ```
 
+```{mermaid}
+gitGraph
+   commit
+   commit
+   branch develop
+   checkout develop
+   commit
+   commit
+   checkout main
+   merge develop
+```
 
-## Hands-on Session! {background-color=var(--dark-bg-color)}
+## Hands-on session {background-color=var(--dark-bg-color)}
 
 1. Create a branch
-2. Rename the branches
-3. Commit something in the branch 
-4. Merge the new branch on master
-5. Check the log for the master branch
-6. Delete the new branch 
+3. Commit something in the branch
+4. Merge the new branch
+5. Check the log for the `main` branch
+6. Delete the new branch (`git branch --help`)
 
-# Rebase a branch
-TODO add drawing 
-- what does it do
+## Conflicts
 
+In collaborative developments people may disagree
 
-```bash
-git rebase master
-```
-
-
-## Hands-on Session! {background-color=var(--dark-bg-color) .leftalign} 
+:::: {.columns}
 
-1. Create `file.txt` in two different branches with this content:
+::: {.column width="30%"}
+
+```{mermaid}
+gitGraph
+   commit
+   commit
+   branch alice
+   checkout alice
+   commit
+   checkout main
+   branch bob
+   checkout bob
+   commit
+```
 
-:::: {.columns}
+:::
 
-::: {.column width="50%"}
+::: {.column width="70%"}
 
+::: {.fragment fragment-index=0}
+Alice fixes an obvious error `file.txt`
 
-```bash 
-# master branch
-echo "Text in master" > file.txt
+```{diff}
+-This course is lame
++This course is nice!
 ```
 :::
 
-::: {.column width="50%"}
+::: {.fragment fragment-index=1}
+Bob is doing the same
 
-```bash 
-# branch b1
-echo "Text in branch" > file.txt
+```{diff}
+-This course is lame
++This course is awesome!
 ```
 :::
 
+:::
+
 ::::
 
-2. Rebase branch b1 on master 
-```bash
-git rebase master
+## Conflicts
+
+This will create a conflict when trying to merge both branches
+
+```{mermaid}
+gitGraph
+   commit
+   commit
+   branch alice
+   checkout alice
+   commit
+   checkout main
+   branch bob
+   checkout bob
+   commit
+   checkout main
+   merge alice
+   merge bob
 ```
 
-3. Edit conflicts 
-```bash
+```{raw}
+Auto-merging file.txt
+CONFLICT (content): Merge conflict in test.txt
+Recorded preimage for 'file.txt'
+Automatic merge failed; fix conflicts and then commit the result.
+```
+
+## Solving conflicts {auto-animate=true}
+
+Solving conflicts requires **your decision**
+
+```{.raw filename=file.txt}
+<<<<<<< HEAD
+This course is nice!
+=======
+This course is awesome!
+>>>>>>> bob
+```
+
+## Solving conflicts {auto-animate=true visibility="uncounted"}
+
+Solving conflicts requires **your decision**
+
+```{.raw filename=file.txt}
+This course is awesome!
+```
+
+:::{.fragment}
+After resolving the conflict, you have to commit your changes
+```{sh}
 git add file.txt
-git rebase --continue
+git commit
 ```
+:::
+
+## Hands-on session {background-color=var(--dark-bg-color) .leftalign} 
+
+1. Create `file.txt` in two different branches with different content
+2. Merge both branches into `main` (CONFLICT!)
+3. Resolve the conflict and commit your changes
 
 
 # Best practices
@@ -205,7 +290,7 @@ git merge
   - ...
 
 
-## Hands-on Session! {background-color=var(--dark-bg-color) .leftalign} 
+## Hands-on session {background-color=var(--dark-bg-color) .leftalign} 
 
 1. Push your repository to GitLab
 2. Add your ssh key to the repository
@@ -213,7 +298,7 @@ git merge
 4. Create a merge request  (add author, reviewer, ...)
 5. Approve and merge it to main 
 
-# Take-home messages!
+# Take home messages
 
 * You should use git daily!
 * Industry is using it as de facto standard
@@ -221,7 +306,43 @@ git merge
 
 # Shotgun buffet
 
-## 
-* useful tools for merge: vscode, meld
-* on Levante: `module load git`
-* documentation links 
\ No newline at end of file
+## Rebase vs merge
+
+Instead of merging branches, one can also [rebase](https://git-scm.com/book/en/v2/Git-Branching-Rebasing)
+
+:::: {.columns}
+
+::: {.column width="50%"}
+```{mermaid}
+%%{init: {'gitGraph': {'showCommitLabel': false}} }%%
+gitGraph
+   commit
+   commit
+   branch develop
+   checkout develop
+   commit
+   commit
+   checkout main
+   commit
+```
+:::
+
+::: {.column width="50%"}
+```{mermaid}
+%%{init: {'gitGraph': {'showCommitLabel': false}} }%%
+gitGraph
+   commit
+   commit
+   commit
+   branch develop
+   checkout develop
+   commit
+   commit
+```
+:::
+
+::::
+Rebasing retains a linear history by **changing the commit history (!!!)**
+
+## Useful tools for merge: vscode, meld
+