> If anything, contributors need a local branch that is then merged to the trunk (unless, somehow, everyone is live-editing the main branch?).
The term originates in the svn or earlier era (hence "trunk"), when "commit" and "push" were the same operation. So there wasn't really such a thing as a local branch, just uncommitted changes. And svn was able to commit changes to any files that no one else had committed to yet, it wasn't whole-repo versioning like git that required you to be fully up-to-date before pushing.
The term originates in the svn or earlier era (hence "trunk"), when "commit" and "push" were the same operation. So there wasn't really such a thing as a local branch, just uncommitted changes. And svn was able to commit changes to any files that no one else had committed to yet, it wasn't whole-repo versioning like git that required you to be fully up-to-date before pushing.