git mergetool is wonderful (in my case, I use kdiff3). However, it is not possible to use it to resolve conflicts from git am or git apply (or even with patch command). Indeed, mergetool need 3 files to work (base and both modified versions) while git am work with a modified version and a patch.
Do you know a way to use git mergetool for conflicts produced with git am?
I think it is necessary to guess the base file from modified version and patch. If you consider each chunk separately, it looks tricky, but not impossible.