AIUI, from the about:config or any other Firefox interface, it is not possible today to clean up preferences, but having more or less preferences does not impact performance or functionality.
From what I know there are no known procedures in how to handle "dead" preferences. I also don't know if the listed preferences are really dead, so I will mark the issue as an enhancement and set component Preferences.
Mike Conley (:mconley) (:⚙️) has approved the revision.
Sören, there were conflicts applying your patch. Please fix and attach the new version.
> If you had done a normal hg pull without --rebase after your hg commit, you will have to first undo that by doing hg rollback.
1) Find the SHA of the commit you want to rebase. I assume this is still where your current working directory is at, so I'd do | hg log | or | hg summary | to get that.
2) Once you have that, I think you can tell Mercurial to rebase that onto "tip" (which should be the most recent commit from central that you'd pulled down).
And that should do it. Then you can | hg update | to tip, and push to Phabricator from there.