--no-pager to Git will tell it to not use a pager. Passing the option
less will tell it to not page if the output fits in a single screen.
git --no-pager diff
Other options from the comments include:
# Set an evaporating environment variable to use 'cat' for your pager GIT_PAGER=cat git diff # Tells 'less' not to paginate if less than a page export LESS="-F -X $LESS" # ...then Git as usual git diff