Use Luacheck as a pre-commit hook

.pre-commit-config.yaml

@@ -7,3 +7,8 @@ repos:
 
       - id: mixed-line-ending
         args: [--fix=lf]
+
+  - repo: https://github.com/Calinou/pre-commit-luacheck
+    rev: v1.0.0
+    hooks:
+      - id: luacheck

.travis.yml

@@ -11,5 +11,5 @@ install:
   - luarocks install --local luacheck
 
 script:
+  # All linters are run with pre-commit hooks
   - $HOME/.local/bin/pre-commit run --all-files
-  - $HOME/.luarocks/bin/luacheck .