Nice to have, just in case, undo and lola :

git config --global alias.undo '!f() { \
    git reset --hard $(git rev-parse --abbrev-ref HEAD)@{${1-1}}; \
}; f'

git config --global alias.lola 'log --graph --decorate --pretty=oneline --abbrev-commit --all'

1. Clone the projet https://github.com/lhoang/metro-git.git
2. Checkout locally all the branches : ligne1, ligne1b, Ligne2, ligne2b, Ligne9 Ex: with git checkout -b ligne1b origin/ligne1b
3. Remove the link with the distant repository

  git remote -v
  git remote rm origin

1. Rename Gare de Lyon
2. Switch Bastille <-> Gare de Lyon
3. Move ligne 2b onto ligne 2 (hint: rebase)
4. Move ligne 1 onto ligne 1 (hint: rebase onto)
5. Create ligne 9a from Franklin D. Roosevelt, add Miromesnil, République, Voltaire
6. Create Nation (hint: Octopus merge)
7. Clean the a and b branches, and finish the ligne 1 and 9.

• Empty commit :

git commit --allow-empty -m "commit message"

• Create Orphan branch :

git checkout --orphan orphan_name
git rm -rf .

• Merge Orphan branch :

git merge orphan_name --allow-unrelated-histories