Add a makefile for helping with style checking and reformatting (#1665)

* Add a makefile

* Add make.bat

* Slightly modify Palm's makefile

* Use make in tox

* Minimise diff and refactor PATHEXT

* Fix a typo in make.bat

Makefile

@@ -0,0 +1,4 @@
+reformat:
+	black -l 99 `git ls-files "*.py"`
+stylecheck:
+	black --check -l 99 `git ls-files "*.py"`

make.bat

@@ -0,0 +1,30 @@
+@echo off
+
+if "%1"=="" goto help
+
+REM This allows us to expand variables at execution
+setlocal ENABLEDELAYEDEXPANSION
+
+REM This will set PYFILES as a list of tracked .py files
+set PYFILES=
+for /F "tokens=* USEBACKQ" %%A in (`git ls-files "*.py"`) do (
+    set PYFILES=!PYFILES! %%A
+)
+
+goto %1
+
+:reformat
+black -l 99 !PYFILES!
+exit /B %ERRORLEVEL%
+
+:stylecheck
+black -l 99 --check !PYFILES!
+exit /B %ERRORLEVEL%
+
+:help
+echo Usage:
+echo   make ^<command^>
+echo.
+echo Commands:
+echo   reformat                   Reformat all .py files being tracked by git.
+echo   stylecheck                 Check which tracked .py files need reformatting.

tox.ini

@@ -8,7 +8,7 @@ envlist =
     py35
     py36
     docs
-    dev
+    style
 
 [testenv]
 description = Run unit tests with pytest
@@ -31,7 +31,13 @@ commands =
 
 [testenv:style]
 description = Stylecheck the code with black to see if anything needs changes.
+whitelist_externals =
+    make
+setenv =
+    # This is just for Windows
+    # Prioritise make.bat over any make.exe which might be on PATH
+    PATHEXT=.BAT;.EXE
 basepython = python3.6
 extras = style
 commands =
-    black -l 99 --check generate_strings.py setup.py tests redbot
+    make stylecheck