Since the '--tidy' option has only been introduced in Texinfo 4.9 More ordinary English syntax would be: Since the '--tidy' option was introduced in Texinfo 4.9
(Though the meaning is clear in the original.) The users should be warned about the planned behavioural change I have the impression that Automake (mostly) uses American English, rather than British English. Since that's where it was created, after all. Hence, I suggest: behavioral. The actual change seems fine to me, FWIW. karl