How to upgrade mattermost running with docker

I'm hosting mattermost-6.3 via docker. I followed this documentation https://docs.mattermost.com/install/install-docker.html and cloned the repository https://github.com/mattermost/docker then I generated the .env file (from env.example) and with docker-compose -f docker-compose.yml -f docker-compose.without-nginx.yml up -d mattermost is up and running.

So far so good, but now I'd like to do an upgrade to v7.4 but I'm finding quite difficult to find a proper documentation on how to do that.

https://docs.mattermost.com/upgrade/prepare-to-upgrade-mattermost.html says what migrations to execute. v6.7, v7.0 and v7.1 are explicitly listed, so that means that I have to first migrate to v6.7, then to v7.0 and then to v7.1? Or can I just apply all the migration at once?

CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_posts_create_at_id on posts(createat, id);
ALTER TABLE reactions ADD COLUMN IF NOT EXISTS channelid varchar(26) NOT NULL DEFAULT '';
UPDATE reactions SET channelid = COALESCE((select channelid from posts where posts.id = reactions.postid), '') WHERE channelid='';
CREATE INDEX CONCURRENTLY IF NOT EXISTS idx_reactions_channel_id on reactions (channelid);

And after executing these SQL command in psql, then what? The next item in the documentation is Upgrading mattermost server but there is no mention here for docker installations. So what should I do next?

• Stop everyting
• git pull
• look at the differences between the .env file and env.example and apply them to .env
• change the MATTERMOST_IMAGE_TAG from 6.3 to 7.4
• execute docker-compose -f docker-compose.yml -f docker-compose.without-nginx.yml up -d

Is that all? Or are there other things to be considered like the postgres version? Like I said, I fail to find a proper documentation of the necessary steps to upgrade when you run with docker.

And what about plugins? Do I need to do something specific to upgrade those too or are they automatically upgraded when you upgrade mattermost?

Am I missing something?

Review the Docker installation guide, the upgrade pages linked in the issue, docker-compose.yml, docker-compose.without-nginx.yml, env.example, and the .env workflow. Document the supported upgrade sequence for the listed Mattermost versions, Docker commands, PostgreSQL considerations, and plugin handling, with steps that can be verified against the requested 6.3-to-7.4 upgrade.