gnu: ocaml: Add ocaml-0install-solver.

* gnu/packages/ocaml.scm (ocaml-0install-solver): New variable.

Change-Id: I52482474746ea518cd108074b0afe22f62952960
Signed-off-by: Julien Lepiller <julien@lepiller.eu>

gnu/packages/ocaml.scm

@@ -992,6 +992,35 @@ https://spdx.github.io/spdx-spec/v2.3/SPDX-license-expressions/
 See https://spdx.org/licenses/ for more details.")
     (license license:expat)))
 
+(define-public ocaml-0install-solver
+  (package
+    (name "ocaml-0install-solver")
+    (version "2.18")
+    (source
+     (origin
+       (method git-fetch)
+       (uri (git-reference
+             (url "https://github.com/0install/0install")
+             (commit (string-append "v" version))))
+       (file-name (git-file-name name version))
+       (sha256
+        (base32 "1hm72k355qwgh16hngmnd77bgawf20ipnqxfncdzl10rqrc0640b"))))
+    (build-system dune-build-system)
+    (arguments
+     `(#:package "0install-solver"))
+    (native-inputs (list ocaml-ounit2))
+    (home-page "https://docs.0install.net/developers/solver/")
+    (synopsis "Package dependency solver")
+    (description
+     "This package provides a package dependency resolver based on a SAT solver.
+This was originally written for the 0install package manager, but is now
+generic and is also used as a solver backend for opam.  The SAT solver is
+based on @code{MiniSat} (http://minisat.se/Papers.html) and the application to
+package management is based on OPIUM (Optimal Package Install/Uninstall
+Manager).  0install-solver uses a (novel?) strategy to find the optimal
+solution extremely quickly (even for a SAT-based solver).")
+    (license license:lgpl2.1+)))
+
 (define ocaml-opam-core
   (package
     (name "ocaml-opam-core")