$ make CHECKED_FILES=it/learning/templates.itely check-translation
ISOLANG= /usr/bin/python -tt ../scripts/auxiliar/check_translation.py
I can't remember and can't find in the archives if there's a solution (some make command to be launched before).
Anyway, I prefer using git:
git <revision> <path>
git diff 67a345f965d169bc1acd23ff4160914fb2142f38 learning/templates.itely
where 67a3... is the committish of the last revision used to translate. The committish copied at the beginning of the translated file.
So this works fine only if the translator knows which version to track from, i.e. if he pasted the specific last commit of the file he updated. This is what I always do (I think that Francisco gave this recommendation to me years ago), but not what the documentation suggests.