According to Unison Manual, using -force <root>:
Including the preference -force root causes Unison to resolve all differences (even non-conflicting changes) in favor of root.
However, I want to force it only in conflicting changes, how can I do it?
I found my answer just after posting, but I would like to keep it here for other people looking into the same problem:
In those cases, you should use "-prefer" instead of "-force" :
That's all :)