This small opam plugin can rewrite opam package definition files to emulate the
behaviour of so-called "lock files" present in many package managers.

It reads opam files, extracts the precise set of their dependencies that is
currently installed, as well as pins and non-installed optional dependencies,
and writes back a <name>.opam.locked file that enforces this set and has the
corresponding pin-depends:.

You can then use opam install <name>.opam.locked to get the package installed
with the precise dependencies, including transitive dependencies, that it had in
the original system.

Option --direct-only can be used to only lock direct dependency versions
rather than the whole tree.

Note that the locked opam file adds conflicts to uninstalled optional
dependencies, but not recursively: it therefore guarantees the same dependencies
get installed, up to potentially some of their optional dependencies.

This project is currently in early beta.