docs: add documentation about using predicate filters

lib/mix/tasks/compile.unused.ex

@@ -69,6 +69,10 @@ defmodule Mix.Tasks.Compile.Unused do
   To ignore warnings about unused structs you need to use "special" syntax in
   form of `{StructModule, :__struct__, 0}`.
 
+  The pattern list can also take the predicate function which can be either
+  unary or binary function. First argument will be `t:mfa/0` and second argument
+  (in case of the binary function) will be `t:MixUnused.Meta.t/0`.
+
   ### Documentation metadata
 
   Functions that have `export: true` in their metadata will be automatically
@@ -77,9 +81,9 @@ defmodule Mix.Tasks.Compile.Unused do
 
   ## Options
 
-  - `severity` - severity of the reported messages, defaults to `hint`.
+  - `--severity` - severity of the reported messages, defaults to `hint`.
     Other allowed levels are `information`, `warning`, and `error`.
-  - `warnings-as-errors` - if the `severity` is set to `:warning` and there is
+  - `--warnings-as-errors` - if the `severity` is set to `:warning` and there is
     any report, then fail compilation with exit code `1`.
   """
 
@@ -152,7 +156,7 @@ defmodule Mix.Tasks.Compile.Unused do
     end
   end
 
-  def update_manifest(data, manifest) do
+  defp update_manifest(data, manifest) do
     cache =
       case File.read(manifest) do
         {:ok, data} -> :erlang.binary_to_term(data)

lib/mix_unused/filter.ex

@@ -19,9 +19,8 @@ defmodule MixUnused.Filter do
 
   @type pattern() :: predicate() | mfa_pattern()
 
-  @doc """
-  Reject values in `exports` that match any pattern in `patterns`.
-  """
+  # Reject values in `exports` that match any pattern in `patterns`.
+  @doc false
   @spec reject_matching(exports :: Exports.t(), patterns :: [pattern()]) ::
           Exports.t()
   def reject_matching(exports, patterns) do

lib/mix_unused/meta.ex

@@ -3,6 +3,16 @@ defmodule MixUnused.Meta do
   Metadata of the functions
   """
 
+  @typedoc """
+  Struct describing function metadata.
+
+  - `:signature` - stringified representation of the function call. Used for display purposes.
+  - `:file` - path to the file that contains definition of given function.
+  - `:line` - integer line number where the function is located within file
+    (currently, it can point to the line where documentation is defined, not
+    exactly to function head).
+  - `:doc_meta` - documentation metadata of the given function.
+  """
   @type t() :: %__MODULE__{
           signature: String.t(),
           file: String.t(),

mix.exs

@@ -29,11 +29,9 @@ defmodule MixUnused.MixProject do
       docs: [
         extras: [
           "CHANGELOG.md": [],
-          LICENSE: [title: "License"],
-          "README.md": [title: "Overview"]
+          LICENSE: [title: "License"]
         ],
-        # main: "Mix.Tasks.Compile.Unused",
-        main: "readme",
+        main: "Mix.Tasks.Compile.Unused",
         source_url: @source_url,
         source_url: "v#{@version}",
         formatters: ["html"]