Fix incompatibility with Neovim < 0.6 for Promise.

Author: kristijanhusak

lua/orgmode/utils/promise.lua

@@ -3,8 +3,18 @@
 local PackedValue = {}
 PackedValue.__index = PackedValue
 
+--- like {...} except preserve the lenght explicitly
+local function pack_len(...)
+  return { n = select('#', ...), ... }
+end
+
+--- like unpack() but use the length set by pack_len if present
+local function unpack_len(t)
+  return unpack(t, 1, t.n)
+end
+
 function PackedValue.new(...)
-  local values = vim.F.pack_len(...)
+  local values = pack_len(...)
   local tbl = { _values = values }
   return setmetatable(tbl, PackedValue)
 end
@@ -17,7 +27,7 @@ function PackedValue.pcall(self, f)
 end
 
 function PackedValue.unpack(self)
-  return vim.F.unpack_len(self._values)
+  return unpack_len(self._values)
 end
 
 function PackedValue.first(self)