Update OPAM file

duff.opam

@@ -1,19 +1,27 @@
-opam-version: "1.2"
+opam-version: "2.0"
 name:         "duff"
 maintainer:   "Romain Calascibetta <[email protected]>"
 authors:      "Romain Calascibetta <[email protected]>"
 homepage:     "https://github.com/dinosaure/duff"
 bug-reports:  "https://github.com/dinosaure/duff/issues"
-dev-repo:     "https://github.com/dinosaure/duff.git"
+dev-repo:     "git+https://github.com/dinosaure/duff.git"
 doc:          "https://dinosaure.github.io/duff/"
 license:      "MIT"
+synopsis:     "Rabin's fingerprint and diff algorithm in OCaml"
+description: """
+This library provides a pure implementation of Rabin's fingerprint and diff algorithm in OCaml.
+
+It follows libXdiff C library. It is used by ocaml-git project.
+"""
 
 build: [
-  ["dune" "subst"] {pinned}
+  ["dune" "subst"]
   ["dune" "build" "-p" name "-j" jobs]
+  ["dune" "runtest" "-p" name "-j" jobs] {with-test}
 ]
 
 depends: [
+  "ocaml"    {>= "4.03.0"}
   "dune"     {build}
   "fmt"
   "cstruct"
@@ -22,7 +30,5 @@ depends: [
   "fmt"      {>= "0.8.5"}
   "bos"      {>= "0.2.0"}
   "fpath"    {>= "0.7.0"}
-  "alcotest" {test}
+  "alcotest" {with-test}
 ]
-
-available: [ocaml-version >= "4.03.0"]