お使いのシステムは最新です状態だった
$ git fetch origin
$ git fetch upstream
From https://github.com/tootsuite/mastodon
c8bf30df9..06f906aca stable-2.9 -> upstream/stable-2.9
* [new tag] v2.9.3 -> v2.9.3
$ git log --oneline upstream/master...origin/master
(なし)
github.comtootsuite/mastodonYour self-hosted, globally interconnected microblogging community - tootsuite/mastodon