.github: Add changelog tip linter

.github/scripts/lint-changelog-tip.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env sh
+
+set -e
+
+CHANGELOG_FILE="docs/victoriametrics/changelog/CHANGELOG.md"
+
+GITHUB_BASE_REF=${GITHUB_BASE_REF:-"master"}
+GIT_REMOTE=${GIT_REMOTE:-"origin"}
+
+git diff "${GIT_REMOTE}/${GITHUB_BASE_REF}"...HEAD -- $CHANGELOG_FILE > diff.txt
+if ! grep -q "^+" diff.txt; then
+  echo "No additions in CHANGELOG.md"
+  exit 0
+fi
+
+ADDED_LINES=$(grep "^+\S" diff.txt | sed 's/^+//')
+
+START_TIP=$(grep -n "^## tip" "$CHANGELOG_FILE" | head -1 | cut -d: -f1)
+if [ -z "$START_TIP" ]; then
+  echo "ERROR: ${CHANGELOG_FILE} does not contain a ## tip section"
+  exit 1
+fi
+
+END_TIP=$(awk "NR>$START_TIP && /^## / {print NR; exit}" "${CHANGELOG_FILE}")
+if [ -z "$END_TIP" ]; then
+  END_TIP=$(wc -l < "$CHANGELOG_FILE")
+fi
+
+BAD=0
+while IFS= read -r line; do
+  # Grep exact line inside the file and get line numbers
+  MATCHES=$(grep -n -F "$line" "$CHANGELOG_FILE" | cut -d: -f1)
+  for m in $MATCHES; do
+    if [ "$m" -lt "$START_TIP" ] || [ "$m" -gt "$END_TIP" ]; then
+      echo "'$line' on line ${m} is outside ## tip section (lines ${START_TIP}-${END_TIP})"
+      BAD=1
+    fi
+  done
+done << EOF
+$ADDED_LINES
+EOF
+
+if [ "$BAD" -ne 0 ]; then
+  echo "CHANGELOG modifications must be placed inside the ## tip section."
+  exit 1
+fi
+
+echo "CHANGELOG modifications are valid."