enable spell check for git message

[iv-nn]

I'm trying to enable spell checking, but for the commit message only.

I tried to set spell for magit buffers and edit the syntax file to add contains=@NoSpell to every other element than commitMsg. I just cannot get it to work for element which already have something in contains=, like gitHunk. I tried to set contains=@diff,@NoSpell but it doesn't work. My understanding is that with this settings it can either contain a @diff element or a @NoSpell element but that doesn't prevent @diff from doing spell checking.

This is where I'm stuck. Do you know if and how this could be achieved ? Also, if it works, would you consider a PR adding this directly to vimagit ?