Fix dependencies of utop dev tool

[gridbugs]

This fixes a bug in computing dependencies of a dev tool package when using dune package management. It only affected the utop dev tool. This change also adds an integration test for the utop dev tool. The test is a github action workflow rather than a cram test so that the real utop package can be tested, since the utop rules have some logic which is specific to the utop package and thus is non-trivial to accurately test with a mock utop package as we do with other dev tool tests.

[Sudha247]

This change looks correct to me. However, how does this affect only utop?

[gridbugs]

This function here (all_deps) is used when communicating dependencies outside of Pkg_rules. Mechanisms for traversing the dependency closure entirely within Pkg_rules are unchanged. However building a utop top level with access to the code in the current project requires an OCAMLPATH with all the dependencies of utop, and the function which computes this (Pkg_rules.dev_tool_ocamlpath) finds dependencies using all_deps.

[shonfeder]

This name doesn't seem accurate to the step, also at least this part is wrong :)

Suggested change

	- name: Set up a project and build it with alice in a nix shell
	- name: Set up a project and build it with dune in a nix shell

[gridbugs]

Haha woops! Fixed.

[Alizter]

Would you mind describing the bug here and why the fix fixes it?

[gridbugs]

Building a utop top level for a project requires knowing the paths to all the libraries that the utop package depends on (e.g.

dune/src/dune_rules/utop.ml

Lines 188 to 197 in 194210a

	let lib_db sctx ~dir =
	let* scope = Scope.DB.find_by_dir dir in
	let* lock_dir_exists = Memo.Lazy.force utop_dev_tool_lock_dir_exists in
	match lock_dir_exists with
	| false -> Memo.return (Scope.libs scope)
	| true ->
	let* ocamlpath = Memo.Lazy.force utop_ocamlpath in
	Lib.DB.of_paths (Super_context.context sctx) ~paths:ocamlpath
	>>| Lib.DB.with_parent ~parent:(Some (Scope.libs scope))
	;;

). When building the utop top level with dune package management, the location of each of utop's dependencies is computed in Pkg_rules and exposed with the function

dune/src/dune_rules/pkg_rules.mli

Line 27 in 194210a

val dev_tool_ocamlpath : Dune_pkg.Dev_tool.t -> Path.t list Memo.t

#12526 changed the representation of dependencies in Pkg_rules allowing dev tools to share dependencies with the default context of the project. I updated Pkg_rules.all_deps (called by Pkg_rules.dev_tool_ocamlpath) to work with this change but introduced a bug where calling it on a dev tool would return the dependencies of the default context of the project rather than the dependencies of the dev tool.

This PR changes all_deps to return the dependencies of a dev tool when it's passed a dev tool rather than returning the dependencies of the project's default context in this case.

[shonfeder]

Thanks for catching the bug and fixing it!