Render manpages into the documentation

The output of every 'odoc cmd --help' is wrapped into code blocks and
concatenated into a page in the documentation.

Author: Julow

doc/dune

@@ -1,3 +1,11 @@
+(rule
+ (action
+  (with-stdout-to
+   manpage.mld
+   (pipe-stdout
+    (run odoc)
+    (run gen_manpage/gen_manpage.exe)))))
+
 (documentation
  (package odoc)
  (mld_files

doc/gen_manpage/dune

@@ -0,0 +1,3 @@
+(executable
+ (name gen_manpage)
+ (libraries astring))

doc/gen_manpage/gen_manpage.ml

@@ -0,0 +1,22 @@
+(** Expect the output of [odoc] on standard input. Called like that, Odoc will
+    output the list of subcommands. *)
+
+open Astring
+
+let gen_preamble _cmds =
+  Printf.printf "{0 Odoc}\n\nOdoc is made of several sub-commands."
+
+let gen_subcommand cmd =
+  Printf.printf "\n{1 odoc %s}\n\n{@man[\n%!" cmd;
+  ignore (Sys.command (Filename.quote_command "odoc" [ cmd; "--help" ]));
+  Printf.printf "]}\n"
+
+let () =
+  let line0 = input_line stdin in
+  let subcommands =
+    match String.cut ~sep:":" line0 with
+    | Some (_, s) -> String.cuts ~sep:"," s |> List.map String.trim
+    | None -> assert false
+  in
+  gen_preamble subcommands;
+  List.iter gen_subcommand subcommands

doc/odoc.mld

@@ -50,6 +50,7 @@ To start contributing to [odoc], please see our {{!page-contributing}contributor
 {1 Page index}
 
 The main other pages of this site:
+- {!page-manpage} Man pages
 - {!page-odoc_for_authors} Odoc For Authors
 - {!page-features} Language Features
 - {!page-driver} Reference Driver