P4merge with GIT 2.18.0

Question

I'm trying to make p4merge works with GIT thanks to this little tutorial

I don't understand what's wrong because I've tried severals ways to do it but I can't succeed in getting a visual interface with p4merge to see the differences between files when I create a merge conflict.

By the way, I'm just using the git bash to type the commands... I don't know if it can be a mistake ?

Here what it wrotes in my .gitconfig :

[diff]
  tool = p4merge
[difftool "p4merge"]
  path = C:\\Program Files\\Perforce\\p4merge.exe
[merge]
  tool = p4merge
[mergetool "p4merge"]
  path = C:\\Program Files\\Perforce\\p4merge.exe

I'm working on Windows 7 and I just typed commands in the tutorial I gave in my post.