How to set up gitconfig to open winmerge without validating each modified file?

I've set up the gitconfig so that difftool uses winmerge to compare file but for each file the command prompt ask me if i want to launch winmerge.

git difftool Viewing (1/7): ###1 Launch 'winmerge' [Y/n]? y

Viewing (2/7): ###2 Launch 'winmerge' [Y/n]? y '###' being filenames

Is there a way to avoid this?

Thanks for your help