Yeah, I know.....
In light of recent events, and the message:
Any errors will be logged to /var/log/nodered-install.log
Alas that gets a bit BIG when looking for an error, or why it didn't update.
(And I shall state I don't know the workings of the directories and why they are used.)
But if /var/log is a directory where logs are stored,
Looking in that directory, there are a lot of files AND directories.
Why not make a Node-Red directory and every time the update/upgrade is done, it makes a new file for that date?
Or, if these updates/upgrades (what ever) etc can happen at any time:
Simply break the log file into 24 hour frames. Each day, new log.
That way if someone's machine spits the dummy, but had been working for weeks, they just need to look at that day's log file.
Just a thought.