local modifications in a submodule would be overwritten the checkout
will fail unless `-f` is used. If nothing (or --no-recurse-submodules)
is used, the work trees of submodules will not be updated.
+ Just like linkgit:git-submodule[1], this will detach the
+ submodules HEAD.
<branch>::
Branch to checkout; if it refers to a branch (i.e., a name that,