Created by: andresgalante
This doesn't resolve #23932 (closed) since the caret still breaks, but it does solve the navbar overflow
It forces the search box to stay inside the navbar container.
@mdo I don't know if this is the most elegant of solutions since we should avoid contextual selectors, but I couldn't think of a better one unless we are willing to remove this line (I still couldn't figure out what it does): https://github.com/twbs/bootstrap/blob/v4-dev/scss/_forms.scss#L325
This is a codepen to show the fix: https://codepen.io/andresgalante/pen/MvNNWe