Preserve upstream policy wording in link examples

internal/doccheck/doccheck_test.go

@@ -12,6 +12,46 @@ import (
 )
 
 var markdownLinkPattern = regexp.MustCompile(`\[[^\]]+\]\(([^)]+)\)`)
+var markdownBackticks = regexp.MustCompile("`+")
+
+// documentationLinks excludes literal examples enclosed by matching backtick
+// runs before applying the existing lightweight link check.
+func documentationLinks(markdown string) [][]string {
+	runs := markdownBackticks.FindAllStringIndex(markdown, -1)
+	text := []byte(markdown)
+	for i := 0; i < len(runs); i++ {
+		width := runs[i][1] - runs[i][0]
+		for j := i + 1; j < len(runs); j++ {
+			if runs[j][1]-runs[j][0] != width {
+				continue
+			}
+			for k := runs[i][0]; k < runs[j][1]; k++ {
+				text[k] = ' '
+			}
+			i = j
+			break
+		}
+	}
+	return markdownLinkPattern.FindAllStringSubmatch(string(text), -1)
+}
+
+func TestDocumentationLinksIgnoreCodeExamples(t *testing.T) {
+	for _, example := range []string{
+		"`[Source](COMMIT_URL).`",
+		"``[Source](COMMIT_URL) with a ` character``",
+		"```markdown\n[Source](COMMIT_URL)\n```",
+	} {
+		t.Run(example, func(t *testing.T) {
+			matches := documentationLinks("[before](before.md) " + example + " [after](after.md)")
+			if len(matches) != 2 || matches[0][1] != "before.md" || matches[1][1] != "after.md" {
+				t.Fatalf("links = %#v, want only the surrounding real links", matches)
+			}
+		})
+	}
+	if matches := documentationLinks("unmatched ` [real](real.md)"); len(matches) != 1 || matches[0][1] != "real.md" {
+		t.Fatalf("unmatched backtick hid a real link: %#v", matches)
+	}
+}
 
 func TestDocumentationLinksResolve(t *testing.T) {
 	root := repositoryRoot(t)
@@ -163,7 +203,7 @@ func walkDocumentationLinks(t *testing.T, root, directory string) {
 		if err != nil {
 			return err
 		}
-		for _, match := range markdownLinkPattern.FindAllStringSubmatch(string(data), -1) {
+		for _, match := range documentationLinks(string(data)) {
 			target := strings.TrimSpace(match[1])
 			if !isLocalDocumentationTarget(target) {
 				continue