Fail CI if the docs are outdated (#961)

* Fail CI if the docs are outdated

* Add and use test that the docs are up to date

* Add EOL

---------

Co-authored-by: Corbin McNeely-Smith <restingbull@mcneely-smith.com>
Co-authored-by: Corbin McNeely-Smith <58151731+restingbull@users.noreply.github.com>

.bazelci/presubmit.yml

@@ -111,6 +111,8 @@ tasks:
     platform: ubuntu1804
     build_targets:
       - //kotlin:stardoc
+    test_targets:
+      - //docs:are_docs_up_to_date_test
   ktlint:
     name: KtLint
     platform: ubuntu1804

docs/BUILD.bazel

@@ -0,0 +1,12 @@
+sh_test(
+    name = "are_docs_up_to_date_test",
+    srcs = ["are_docs_up_to_date_test.sh"],
+    args = [
+        "$(location kotlin.md)",
+        "$(location //kotlin:stardoc)",
+    ],
+    data = [
+        "kotlin.md",
+        "//kotlin:stardoc",
+    ],
+)

docs/are_docs_up_to_date_test.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+function fail {
+  echo >&2 "#####   $1   ######"
+  exit 1
+}
+
+current="$1"
+new="$2"
+[[ -f $new ]] || fail "missing new docs"
+[[ -f $current ]] || fail "missing current docs"
+
+diff -u "$1" "$2" || fail "kotlin docs are out of date"