Mon dieu! You mean dogs in France speak French too. No wonder my two look at me strangely when I talk to them in English.
Odd as it may seem, despite the number of dog encounters I have witnessed on my club rides, nobody has ever shouted anything. They simply laugh and remark about the 'foolish dog' or some such, but nothing in anger. As a warning, you'll hear 'attention' or 'faire attention'.
As a not so interesting aside, some folk might know of the 'car up / car down' warning in the UK. I could never remember which direction was 'up' and which was 'down'... most confusing. (It's also t'other way around in the US. That is, where in the UK you'd say 'car up' they'd say 'car down' in the US... summat like that anyway). Not a problem in France, as it's 'car ahead' (voiture d'avant) or 'car behind' (voiture d'arriere). Note also that "car" in French is a bus... just in case you hear 'car d'arriere'!