tests: add test for checking first line of a file

Abirdcfly · Abirdcfly · commit f64710e649fd · 2022-10-24T10:25:04.000+08:00
diff --git a/testdata/src/a/doc.go b/testdata/src/a/doc.go
@@ -0,0 +1,2 @@
+// Package a this comment include duplicated word and and // want `Duplicate words \(and\) found`
+package a

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+// Package a this comment include duplicated word and and // want `Duplicate words \(and\) found`
	`2`	`+package a`