undent: last char was omitted when last line was "\n\t\t}"

Because of a mistake I made in the indexing, the "case 1" was only
checking that all the remaining chars in the last line but the last char
was made of indentation: in the example in the commit title, it was
looking at "\t\t" rather than "\t\t}", thus wrongly going in the "case 1".

Author: maelvls

pkg/testutil/undent.go

@@ -122,7 +122,7 @@ func Undent(s string) string {
 
 		// Case 1: we want the user to be able to omit some tabs or spaces in
 		// the last line for readability purposes.
-		case line == len(lineOffsets)-1 && s[last] != '\n' && isIndent(s[first:last]):
+		case line == len(lineOffsets)-1 && s[last] != '\n' && isIndent(s[first:last+1]):
 			lineStr = ""
 
 		// Case 2: we want the user to be able to omit the indentations for

pkg/testutil/undent_test.go

@@ -34,6 +34,7 @@ func Test_Undent(t *testing.T) {
 
 		bar
 	`, "foo\n\nbar\n"))
+	t.Run("bug fix: last char is not omitted", runTest_Undent("\t\t{\n\t\t    \"kind\": \"Secret\"\n\t\t}", "{\n    \"kind\": \"Secret\"\n}"))
 }
 
 func runTest_Undent(given, expected string) func(t *testing.T) {