Michele Ballabio [off-list ref] writes:
+-f::
+--force-rebase::
+ Force the rebase even if the current branch is up to date.
+ Normally, if the current branch is up to date, the rebase is
+ aborted.
+
For the sake of brevity we say "up to date" in the error message from the
command, but for people who looks up the manual to figure out why their
rebase is not rebasing with that error message, we may want to explain
what the phrase means in this context. E.g.
... even if the branch is a descendant of the commit you are
rebasing onto. Normally the command will exit with a message
"Current branch is up to date" in such a situation.