userdiff: add Elixir to supported userdiff languages

Adds support for xfuncref in Elixir[1] language which is Ruby-like
language that runs on Erlang[3] Virtual Machine (BEAM).

[1]: https://elixir-lang.org
[2]: https://www.erlang.org

Signed-off-by: Łukasz Niemier <lukasz@niemier.pl>
Acked-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/gitattributes.txt

@@ -812,6 +812,8 @@ patterns are available:
 
 - `dts` suitable for devicetree (DTS) files.
 
+- `elixir` suitable for source code in the Elixir language.
+
 - `fortran` suitable for source code in the Fortran language.
 
 - `fountain` suitable for Fountain documents.

t/t4018-diff-funcname.sh

@@ -32,6 +32,7 @@ diffpatterns="
 	csharp
 	css
 	dts
+	elixir
 	fortran
 	fountain
 	golang

t/t4018/elixir-do-not-pick-end

@@ -0,0 +1,5 @@
+defmodule RIGHT do
+end
+#
+#
+# ChangeMe; do not pick up 'end' line

t/t4018/elixir-ex-unit-test

@@ -0,0 +1,6 @@
+defmodule Test do
+  test "RIGHT" do
+    assert true == true
+    assert ChangeMe
+  end
+end

t/t4018/elixir-function

@@ -0,0 +1,5 @@
+def function(RIGHT, arg) do
+  # comment
+  # comment
+  ChangeMe
+end

t/t4018/elixir-macro

@@ -0,0 +1,5 @@
+defmacro foo(RIGHT) do
+  # Code
+  # Code
+  ChangeMe
+end

t/t4018/elixir-module

@@ -0,0 +1,9 @@
+defmodule RIGHT do
+  @moduledoc """
+  Foo bar
+  """
+
+  def ChangeMe(a) where is_map(a) do
+    a
+  end
+end

t/t4018/elixir-module-func

@@ -0,0 +1,8 @@
+defmodule Foo do
+  def fun(RIGHT) do
+     # Code
+     # Code
+     # Code
+     ChangeMe
+  end
+end

t/t4018/elixir-nested-module

@@ -0,0 +1,9 @@
+defmodule MyApp.RIGHT do
+  @moduledoc """
+  Foo bar
+  """
+
+  def ChangeMe(a) where is_map(a) do
+    a
+  end
+end

t/t4018/elixir-private-function

@@ -0,0 +1,5 @@
+defp function(RIGHT, arg) do
+  # comment
+  # comment
+  ChangeMe
+end

t/t4018/elixir-protocol

@@ -0,0 +1,6 @@
+defprotocol RIGHT do
+  @doc """
+  Calculates the size (and not the length!) of a data structure
+  """
+  def size(data, ChangeMe)
+end

t/t4018/elixir-protocol-implementation

@@ -0,0 +1,5 @@
+defimpl RIGHT do
+  # Docs
+  # Docs
+  def foo(ChangeMe), do: :ok
+end

userdiff.c

@@ -32,6 +32,18 @@ PATTERNS("dts",
 	 /* Property names and math operators */
 	 "[a-zA-Z0-9,._+?#-]+"
 	 "|[-+*/%&^|!~]|>>|<<|&&|\\|\\|"),
+PATTERNS("elixir",
+	 "^[ \t]*((def(macro|module|impl|protocol|p)?|test)[ \t].*)$",
+	 /* Atoms, names, and module attributes */
+	 "|[@:]?[a-zA-Z0-9@_?!]+"
+	 /* Numbers with specific base */
+	 "|[-+]?0[xob][0-9a-fA-F]+"
+	 /* Numbers */
+	 "|[-+]?[0-9][0-9_.]*([eE][-+]?[0-9_]+)?"
+	 /* Operators and atoms that represent them */
+	 "|:?(\\+\\+|--|\\.\\.|~~~|<>|\\^\\^\\^|<?\\|>|<<<?|>?>>|<<?~|~>?>|<~>|<=|>=|===?|!==?|=~|&&&?|\\|\\|\\|?|=>|<-|\\\\\\\\|->)"
+	 /* Not real operators, but should be grouped */
+	 "|:?%[A-Za-z0-9_.]\\{\\}?"),
 IPATTERN("fortran",
 	 "!^([C*]|[ \t]*!)\n"
 	 "!^[ \t]*MODULE[ \t]+PROCEDURE[ \t]\n"