Merge branch 'so/rebase-doc' into maint

* so/rebase-doc:
  Documentation/git-rebase.txt: <upstream> must be given to specify <branch>
  Documentation/git-rebase.txt: -f forces a rebase that would otherwise be a no-op

Documentation/git-rebase.txt

@@ -9,7 +9,7 @@ SYNOPSIS
 --------
 [verse]
 'git rebase' [-i | --interactive] [options] [--exec <cmd>] [--onto <newbase>]
-	[<upstream>] [<branch>]
+	[<upstream> [<branch>]]
 'git rebase' [-i | --interactive] [options] [--exec <cmd>] [--onto <newbase>]
 	--root [<branch>]
 'git rebase' --continue | --skip | --abort | --edit-todo
@@ -316,11 +316,8 @@ which makes little sense.
 
 -f::
 --force-rebase::
-	Force the rebase even if the current branch is a descendant
-	of the commit you are rebasing onto.  Normally non-interactive rebase will
-	exit with the message "Current branch is up to date" in such a
-	situation.
-	Incompatible with the --interactive option.
+	Force a rebase even if the current branch is up-to-date and
+	the command without `--force` would return without doing anything.
 +
 You may find this (or --no-ff with an interactive rebase) helpful after
 reverting a topic branch merge, as this option recreates the topic branch with