NOTE: This is addressing UPDATING your current setup, not changing from, for instance, latest to nightly.
The update method depends on how you installed it.
I'm running locally and got the code by downloading the zip file:
Download a new zip file, uncompress it, and move your config dir into that new directory. Reinstall requirements.
This is the "fussiest" method of update.
I'm running locally and retrieved the code via git:
cd DIRECTORY_WHERE_YOU_PUT_PMM
git checkout BRANCH_NAME
git stash
git stash clear
git pull
For BRANCH_NAME, substitute master, develop, or nightly
You may need to reinstall requirements if switching branch or updating to a new major version:
python -m pip install -r requirements.txt
Those stash commands are going to discard any changes you may have made to PMM's own files. If that's a concern, you are probably familiar enough with git to know what you need to do instead.
I'm using docker locally:
docker pull meisnate12/plex-meta-manager:TAG_HERE
replace TAG_HERE with latest, develop, or nightly
Then recreate your container via whatever means you used to create it [docker run, docker-compose, etc.].
I'm using docker on a NAS or some other remote context:
Update the image using whatever means the NAS provides.
Depending on the system, this might be a simple rebuild of the container, or you may need to manually pull the new image first.