Add a new --latests-only option to opam list & opam admin list to onl…

…y work on the set of latest packages

src/client/opamArg.ml

@@ -1594,16 +1594,21 @@ let package_selection cli =
       "Only includes packages which have the given tag set"
       Arg.string
   in
+  let latests_only =
+    mk_flag ~cli (cli_from cli2_2) ["latests-only"]  ~section
+      "List only the latest version of each package."
+  in
   let filter
       depends_on required_by conflicts_with coinstallable_with resolve
       recursive depopts nobuild post dev doc_flag test dev_setup field_match
-      has_flag has_tag
+      has_flag has_tag latests_only
     =
     let dependency_toggles = {
       OpamListCommand.
       recursive; depopts; build = not nobuild; post; test; dev_setup;
       doc = doc_flag; dev
     } in
+    (if latests_only then [OpamListCommand.Latests_only] else []) @
     List.map (fun flag -> OpamListCommand.Flag flag) has_flag @
     List.map (fun tag -> OpamListCommand.Tag tag) has_tag @
     List.map (fun (field,patt) ->
@@ -1632,7 +1637,7 @@ let package_selection cli =
         depends_on $ required_by $ conflicts_with $ coinstallable_with $
         resolve $ recursive $ depopts $ nobuild $ post cli $ dev cli $
         doc_flag cli $ test cli $ dev_setup cli $ field_match $ has_flag $
-        has_tag)
+        has_tag $ latests_only)
 
 let package_listing_section = "OUTPUT FORMAT OPTIONS"
 

src/client/opamListCommand.ml

@@ -64,6 +64,7 @@ type selector =
   | Available
   | Installable
   | Pinned
+  | Latests_only
   | Depends_on of dependency_toggles * atom list
   | Required_by of dependency_toggles * atom list
   | Conflicts_with of package list
@@ -86,6 +87,7 @@ let string_of_selector =
   | Available -> "available" % `cyan
   | Installable -> "installable" % `cyan
   | Pinned -> "pinned" % `cyan
+  | Latests_only -> "latest-only" % `cyan
   | Depends_on (tog,atoms) ->
     Printf.sprintf "%s(%s)"
       ((if tog.recursive then "rec-depends-on" else "depends-on") % `blue)
@@ -222,6 +224,11 @@ let apply_selector ~base st = function
       (OpamSwitchState.universe st ~requested:OpamPackage.Set.empty Query)
       base
   | Pinned -> OpamPinned.packages st
+  | Latests_only ->
+    OpamPackage.to_map base |>
+    OpamPackage.Name.Map.map (fun vset ->
+      OpamPackage.Version.Set.singleton (OpamPackage.Version.Set.max_elt vset)) |>
+    OpamPackage.of_map
   | (Required_by ({recursive=true; _} as tog, atoms)
     | Depends_on ({recursive=true; _} as tog, atoms)) as direction ->
     let deps_fun = match direction with

src/client/opamListCommand.mli

@@ -49,6 +49,7 @@ type selector =
   | Available
   | Installable
   | Pinned
+  | Latests_only
   | Depends_on of dependency_toggles * atom list
   | Required_by of dependency_toggles * atom list
   | Conflicts_with of package list