docs: enable markdown linting

Makefile

@@ -9,6 +9,8 @@ IMAGE_BUILD_EXTRA_OPTS ?=
 IMAGE_PUSH_CMD ?= docker push
 CONTAINER_RUN_CMD ?= docker run
 
+MDL ?= mdl
+
 # Docker base command for working with html documentation.
 # Use host networking because 'jekyll serve' is stupid enough to use the
 # same site url than the "host" it binds to. Thus, all the links will be
@@ -117,6 +119,9 @@ gofmt-verify:
 ci-lint:
 	golangci-lint run --timeout 5m0s
 
+mdlint:
+	find docs/ -path docs/vendor -prune -false -o -name '*.md' | xargs $(MDL) -s docs/mdl-style.rb
+
 test:
 	$(GO_CMD) test ./cmd/... ./pkg/...
 

docs/mdl-style.rb

@@ -0,0 +1,6 @@
+all
+# Exclude MD041 - First line in file should be a top level header
+exclude_rule 'MD041'
+rule 'MD013', :tables => false
+rule 'MD013', :code_blocks => false
+rule 'MD024', :allow_different_nesting => true

scripts/test-infra/mdlint.sh

@@ -0,0 +1,7 @@
+#!/bin/bash -e
+
+# Install mdl
+gem install mdl -v 0.11.0
+
+# Run verify steps
+make mdlint