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