I installed opam from a fresh start (reinstalled opam itself, deleted my
.opam), ran "opam switch 4.01.0", and then tried to install ocp-indent,
which installed version 0.1.0. So I tried opam upgrade, which wanted to
install 0.6.1 even though there are later versions available:

$ opam upgrade
The following actions will be performed:
 - upgrade ocp-indent.0.1.0 to 0.6.1
0 to install | 0 to reinstall | 1 to upgrade | 0 to downgrade | 0 to remove

=-=-= Removing Packages =-=-=
Removing ocp-indent.0.1.0.
  ./configure --prefix=/home/martin/.opam/4.01.0
  make uninstall

=-=-= Installing ocp-indent.0.6.1 =-=-=

.....

$ opam install ocp-indent
[NOTE] Package ocp-indent is already installed (current version is 0.6.1).

$ opam install ocp-indent.1.4.1
The following actions will be performed:
 - install ocamlfind.1.5.2 [required by ocp-indent]
 - install cmdliner.0.9.5 [required by ocp-indent]
 - install typerex.1.99.6-beta [required by ocp-indent]
 - install ocp-build.1.99.6-beta [required by ocp-indent]
 - upgrade ocp-indent.0.6.1 to 1.4.1
4 to install | 0 to reinstall | 1 to upgrade | 0 to downgrade | 0 to remove
Do you want to continue ? [Y/n] y