it's not well documented in the git integration document that ots-git-gpg-wrapper.sh should be installed from https://raw.githubusercontent.com/opentimestamps/opentimestamps-client/master/ots-git-gpg-wrapper.sh

I think it would be easier to follow if the url is explicitly mentioned in the instructions.
Something like this would be helpful and save some time:

cd ~
wget https://raw.githubusercontent.com/opentimestamps/opentimestamps-client/master/ots-git-gpg-wrapper.sh
git config --global gpg.program ~/ots-git-gpg-wrapper.sh