This page shows the git clone command, but doesn’t indicate what directory to run it from. I ask this because shell scripts such as this seem to assume that they live in a directory at / named openmrs (not openmrs-core). E.g., line 10 of that script is source /openmrs/startup-init.sh.
That shell script is entirely for use in the Docker container and shouldn’t be used outside of it. Generally, what directory you clone the repo in doesn’t matter, but it should be a directory that does not contain spaces.