- get a copy of the folder we created
 - run: git log
 - run: gitk
 - run: git checkout "le commit initial"
 - edit: paper.tex (and keep your editor open)
 -- change: intro to something shorter
 -- change: some other part to something shorter
 - run: git commit
 - run: gitk (just init + this)
 - run: gitk --all (all named, not this)
 - run: git checkout -b shorter
   - when you do that, your open editor should tell
     you that the file changed, right away or when
     you try to change edit the file. If it does not
     change your editor for something better/safer.
 - run: gitk --all (all named)

 - run: git checkout master
 - run: gitk --all (it is bold that moved)
 - run: git merge shorter
 - run: gitk --all

 - run: git checkout master # already on it
 - run: git checkout -b pig
 - add the pig image
 - edit:
 -- change the title
 -- replace the bird with a pig
 - commit it

 - run: git checkout master
 - edit:
 -- go from one bird to 3 birds
\includegraphics[width=2.5cm]{a_bird.png}
\includegraphics[width=3cm]{a_bird.png}
\includegraphics[width=2cm]{a_bird.png}
 -- modify something else
 - commit
 - run: gitk --all

 - run: git merge pig (conflict)
 - run: git status
 - run: git gui    (to have a look)
 - run: gitk --all (in progress)
 - open and fix (look at title, modif part and the conflict)
 - run: pdflatex paper.tex
 - run: git status
 - run: git add paper.tex
 - run: git commit