opam admin upgrade does for whole repository, this tiny tool is a more convenient way to migrate individual opam files (or all the files in a project).
opam package-upgrade [opam|NAME.opam|DIR...]
This is just a step in the ongoing migration to opam 2.0.
Note that, if you use opam 2.0 beta already, the
opam files are migrated internally upon pinning the packge: keeping your source-tracked
opam files in
1.2 format remains the more compatible option if you don’t need the new features.