Enable fast8 check

Fast8 only check these files that changed, which is more efficient for tox test.

Change-Id: I9a9816e12361900261fa2ee693bf211154eb2e0f

tools/flake8wrap.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+#
+# A simple wrapper around flake8 which makes it possible
+# to ask it to only verify files changed in the current
+# git HEAD patch.
+#
+# Intended to be invoked via tox:
+#
+#   tox -epep8 -- -HEAD
+#
+
+if test "x$1" = "x-HEAD" ; then
+    shift
+    files=$(git diff --name-only HEAD~1 | tr '\n' ' ')
+    echo "Running flake8 on ${files}"
+    echo ""
+    echo "Consider using the 'pre-commit' tool instead."
+    echo ""
+    echo "    pip install --user pre-commit"
+    echo "    pre-commit install --allow-missing-config"
+    echo ""
+    diff -u --from-file /dev/null ${files} | flake8 --diff "$@"
+else
+    echo "Running flake8 on all files"
+    echo ""
+    exec flake8 "$@"
+fi
+

tox.ini

@@ -10,6 +10,12 @@ basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          OS_TEST_PATH=venus/tests/unit
 usedevelop = True
+allowlist_externals =
+  bash
+  find
+  rm
+  env
+  make
 install_command = pip install {opts} {packages}
 
 deps =
@@ -30,6 +36,13 @@ commands =
   # Check that .po and .pot files are valid:
   doc8 --ignore D001  doc/source/ CONTRIBUTING.rst HACKING.rst README.rst
 
+[testenv:fast8]
+description =
+  Run style checks on the changes made since HEAD~. For a full run including docs, use 'pep8'
+envdir = {toxworkdir}/shared
+commands =
+  bash tools/flake8wrap.sh -HEAD
+
 [testenv:venv]
 commands = {posargs}