generator: Add a function to find an action by name.

Fairly simple refactoring.

generator/actions.ml

@@ -187,3 +187,8 @@ let fish_functions = List.filter is_fish
  * alphabetically, so this is useful:
  *)
 let sort = List.sort action_compare
+
+(* Find a single action by name, or give an error. *)
+let find name =
+  try List.find (fun { name = n } -> n = name) actions
+  with Not_found -> failwithf "could not find action named '%s'" name

generator/actions.mli

@@ -47,6 +47,10 @@ val sort : Types.action list -> Types.action list
 (** Sort the functions alphabetically by name
     (see also {!Utils.action_compare}). *)
 
+val find : string -> Types.action
+(** Find an action by name.  If it doesn't exist, this fails with an
+    error. *)
+
 val is_documented : Types.action -> bool
 (** Returns true if function should be documented, false otherwise. *)
 

generator/tests_c_api.ml

@@ -380,10 +380,7 @@ and generate_test_command_call ?(expect_error = false) ?(do_return = true) ?test
     match cmd with [] -> assert false | name :: args -> name, args in
 
   (* Look up the function. *)
-  let f =
-    try List.find (fun { name = n } -> n = name) actions
-    with Not_found ->
-      failwithf "%s: in test, command %s was not found" test_name name in
+  let f = Actions.find name in
 
   (* Look up the arguments and return type. *)
   let style_ret, style_args, style_optargs = f.style in