Great video with soldiers from Leclerc's 2nd Armored Division assault the Hotel Majestic in August 1944 and capturing many Germans after negociation with an officer. Note pows are treated fairly . German prisoners in France 1944 - YouTube
I would think that the willingness of the German commander of Paris to surrender the city without burning it to the ground as ordered by Hitler would have had some positive impact on the treatment of at least Wehrmacht soldiers willing to surrender afterwards. Indeed I don't think I've read many accounts of the French mistreating Nazi prisoners except for some of the post war accounts.
I've always believed the easiest way to avoid bloodshed and win a war is to take prisoners and treat them fairly, whilst having a reputation as a great and fierce fighting force. If the enemy believes that being taken prisoner is a better option than fighting it out, why wouldn't they surrender. Mistreating prisoners will only encourage them to fight harder.