Workflow for opam Packages

This feature is experimental

This feature didn't receive a lot of testing, please report any issues found and feature requests.

esy supports developing opam projects directly, the workflow is similar to esy projects:

% git clone https://github.com/rgrinberg/ocaml-semver.git
% cd ocaml-semver
% esy install
% esy build

Installing dependencies

To install project dependencies run esy install command.

This will read dependencies from all *.opam files found in a project and install them locally into the sandbox.

Note that even compiler is installed locally to the project, you don't need to manage switches manually like in opam:

% esy ocamlc

Will run the compiler version defined by the project's constraints set in *.opam files.

To build project dependencies and the project itself run esy build command.

The esy build command performs differently depending on the number of opam files found in a project directory:

In case there's a single *.opam file found esy build will build all dependencies and then execute build commands found in opam metadata.
In case there are multiple *.opam files found esy build will build all dependencies and stop. To build the project itself users are supposed to use the command which is specified by the project's workflow but run inside the esy's build environment.

In case of a dune-based project this is usually means:
```
% esy b dune build
```