py-topdir.mk: Add file

Add a file to be included from every toplevel Makefile of every repo that owns Python code. It defines the following targets:
py-check: py-check-syntax py-check-format py-check-syntax: py-check-format: py-format:
Currently, only mypy is run from py-check-syntax, but the targets are meant as entry point for further linter jobs in the future.
There's also
py-format-assignments:
which is meant to add spaces around "=" in multi-line assignment blocks, but, pending future experiments, I thing that target is going to be removed again. Left in for now.
Signed-off-by: Jan Lindemann <jan@janware.com>

make/py-topdir.mk

@@ -0,0 +1,31 @@
+TD_COPY_FILES               +=
+
+PY_CHECK_EXCLUDE            ?=
+PY_SRC_ROOT                 += $(wildcard $(TOPDIR)/src $(TOPDIR)/tools)
+
+all:
+
+format: py-format
+check-syntax: py-check-syntax
+check-format: py-check-format
+
+py-check: py-check-syntax py-check-format
+py-check-syntax:
+	mypy $(addprefix --exclude ,$(PY_CHECK_EXCLUDE)) $(PY_SRC_ROOT)
+
+py-check-format:
+
+py-format:
+	find . -type f -name '*.py' -print0 | \
+		xargs -0 sed -i -E '1{/^# -\*- coding: utf-8 -\*-$$/{:a;N;/\n[[:space:]]*$$/ba;s/^# -\*- coding: utf-8 -\*-\n([[:space:]]*\n)*/ /;s/^ //}}'
+
+py-format-assignments:
+	find . \
+	  -path './.git' -prune -o \
+	  -type f -name '*.py' \
+	  -execdir /usr/bin/sed -i 's/^\(\s\+[a-zA-Z0-9_]\+\)=\([^,[:space:]]\+\)\([,(]\)*\s*$$/\1 = \2\3/g' {} '+'
+	git diff --exit-code
+
+clean.topdir: clean.py-check
+clean.py-check:
+	rm -rf .mypy_cache