Something wrong

git reflog
# you will see a list of every thing you've done in git, across all branches!
# each one has an index HEAD@{index}
# find the one before you broke everything
git reset HEAD@{index}
# magic time machine

I accidentally committed to the wrong branch!

# undo the last commit, but leave the changes available
git reset HEAD~ --soft
git stash
# move to the correct branch
git checkout name-of-the-correct-branch
git stash pop
git add . # or add individual files
git commit -m "your message here"
# now your changes are on the correct branch

Oui, quelqu'un paie un nom de domaine chaque année pour ça. Merci quand même :-)