tests: python: add ruff

When looking at 'ynl', 'ruff' found out at least one interesting error:
one variable was used but not defined.

It looks then interesting to add it. Its usage is very similar to
pylint. Some says it can also be used instead of pylint, but I'm not
experienced enough to judge.

Note that by default, ruff will only check for "interesting" errors.

Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

Author: matttbe

tests/patch/ruff/info.json

@@ -0,0 +1,3 @@
+{
+  "run": ["ruff.sh"]
+}

tests/patch/ruff/ruff.sh

@@ -0,0 +1,60 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+HEAD=$(git rev-parse HEAD)
+rc=0
+
+pr() {
+    echo " ====== $* ======" | tee -a /dev/stderr
+}
+
+# If it doesn't touch .py files, don't bother. Ignore deleted.
+if ! git show --diff-filter=AM --pretty="" --name-only "${HEAD}" | grep -q -E "\.py$"
+then
+    echo "No python scripts touched, skip" >&"$DESC_FD"
+    exit 0
+fi
+
+ruff --version || exit 1
+
+tmpfile_o=$(mktemp)
+tmpfile_n=$(mktemp)
+
+echo "Redirect to $tmpfile_o and $tmpfile_n"
+
+echo "Tree base:"
+git log -1 --pretty='%h ("%s")' HEAD~
+echo "Now at:"
+git log -1 --pretty='%h ("%s")' HEAD
+
+pr "Checking before the patch"
+git checkout -q HEAD~
+
+# Also ignore created, as not present in the parent commit
+for f in $(git show --diff-filter=M --pretty="" --name-only "${HEAD}" | grep -E "\.py$"); do
+    ruff check --output-format pylint "$f" | tee -a "$tmpfile_o"
+done
+
+incumbent=$(wc -l < "$tmpfile_o")
+
+pr "Checking the tree with the patch"
+git checkout -q "$HEAD"
+
+for f in $(git show --diff-filter=AM --pretty="" --name-only "${HEAD}" | grep -E "\.py$"); do
+    ruff check --output-format pylint "$f" | tee -a "$tmpfile_n"
+done
+
+current=$(wc -l < "$tmpfile_n")
+
+echo "Errors before: $incumbent ; this patch: $current" >&"$DESC_FD"
+
+if [ "$current" -gt "$incumbent" ]; then
+    echo "New errors added" 1>&2
+    diff -U 0 "$tmpfile_o" "$tmpfile_n" 1>&2
+
+    rc=1
+fi
+
+rm "$tmpfile_o" "$tmpfile_n"
+
+exit $rc