the local merge commits are included in the rebase (see
linkgit:git-rebase[1] for details).
+
-When set to preserve, rebase with the `--preserve-merges` option passed
-to `git rebase` so that locally created merge commits will not be flattened.
+When set to `preserve` (deprecated in favor of `merges`), rebase with the
+`--preserve-merges` option passed to `git rebase` so that locally created
+merge commits will not be flattened.
+
When false, merge the current branch into the upstream branch.
+