+Without '--force', the <src> ref is stored at the remote only if
+<dst> does not exist, or <dst> is a proper subset (i.e. an
+ancestor) of <src>. This check, known as "fast forward check",
+is performed in order to avoid accidentally overwriting the
+remote ref and lose other peoples' commits from there.
+
+With '--force', the fast forward check is disabled for all refs.
+
+Optionally, a <ref> parameter can be prefixed with a plus '+' sign
+to disable the fast-forward check only on that ref.
+