Add naive and untested version of Lua language support.

testing/gen-languages-all

@@ -3,7 +3,7 @@ import sys
 
 LANGUAGES = [
     'conda', 'coursier', 'dart', 'docker', 'docker_image', 'dotnet', 'fail',
-    'golang', 'node', 'perl', 'pygrep', 'python', 'r', 'ruby', 'rust',
+    'golang', 'lua', 'node', 'perl', 'pygrep', 'python', 'r', 'ruby', 'rust',
     'script', 'swift', 'system',
 ]
 FIELDS = [

testing/get-lua.sh

@@ -0,0 +1,5 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Install the runtime and package manager.
+sudo apt install lua5.3 liblua5.3-dev luarocks

testing/resources/lua_repo/.pre-commit-hooks.yaml

@@ -0,0 +1,4 @@
+-   id: hello-world-lua
+    name: hello world lua
+    entry: hello-world-lua
+    language: lua

testing/resources/lua_repo/bin/hello-world-lua

@@ -0,0 +1,3 @@
+#!/usr/bin/env lua
+
+print('hello world')

testing/resources/lua_repo/hello-dev-1.rockspec

@@ -0,0 +1,15 @@
+package = "hello"
+version = "dev-1"
+
+source = {
+   url = "git+ssh://git@github.com/pre-commit/pre-commit.git"
+}
+description = {}
+dependencies = {}
+build = {
+    type = "builtin",
+    modules = {},
+    install = {
+        bin = {"bin/hello-world-lua"}
+    },
+}

testing/util.py

@@ -48,6 +48,10 @@ skipif_cant_run_docker = pytest.mark.skipif(
     os.name == 'nt' or not docker_is_running(),
     reason="Docker isn't running or can't be accessed",
 )
+skipif_cant_run_lua = pytest.mark.skipif(
+    os.name == 'nt',
+    reason="lua isn't installed or can't be found",
+)
 skipif_cant_run_swift = pytest.mark.skipif(
     parse_shebang.find_executable('swift') is None,
     reason="swift isn't installed or can't be found",