Add default target and remove configurable venv paths

Signed-off-by: Jose R. Gonzalez <komish@flutes.dev>

scripts/Makefile

@@ -1,21 +1,32 @@
 PY_BIN ?= python3
 
-VENV_CODESTYLE ?= venv.codestyle
+# The virtualenv containing code style tools.
+VENV_CODESTYLE = venv.codestyle
 VENV_CODESTYLE_BIN = $(VENV_CODESTYLE)/bin
 
-VENV_TOOLS ?= venv.tools
+# The virtualenv containing our CI scripts
+VENV_TOOLS = venv.tools
 VENV_TOOLS_BIN = $(VENV_TOOLS)/bin
 
 # This is what we pass to git ls-files.
 LS_FILES_INPUT_STR ?= 'src/*.py'
 
+.PHONY: default
+default: format lint
+
 # The same as format, but will throw a non-zero exit code
 # if the formatter had to make changes.
 .PHONY: ci.format
 ci.format: format
 	git diff --exit-code
 
 venv.codestyle:
+	$(MAKE) venv.codestyle.always-reinstall
+
+# This target will always install the codestyle venv.
+# Useful for development cases.
+.PHONY: venv.codestyle.always-reinstall
+venv.codestyle.always-reinstall:
 	$(PY_BIN) -m venv $(VENV_CODESTYLE)
 	./$(VENV_CODESTYLE_BIN)/pip install --upgrade \
 		black \
@@ -34,6 +45,12 @@ lint: venv.codestyle
 		$$(git ls-files $(LS_FILES_INPUT_STR))
 
 venv.tools:
+	$(MAKE) venv.tools.always-reinstall
+
+# This target will always install the tools at the venv.
+# Useful for development cases.
+.PHONY: venv.tools.always-reinstall
+venv.tools.always-reinstall:
 	$(PY_BIN) -m venv $(VENV_TOOLS)
 	./$(VENV_TOOLS_BIN)/pip install -r requirements.txt
-	./$(VENV_TOOLS_BIN)/python setup.py install
+	./$(VENV_TOOLS_BIN)/python setup.py install