Re: [PATCH 3/3] index: do not warn about unrecognized extensions

[Junio C Hamano <gitster@pobox.com>]

Jonathan Nieder <jrnieder@gmail.com> writes:

> We cannot change the past, but for index extensions of the future,
> there is a straightforward improvement: silence that message except
> when tracing.  This way, the message is still available when
> debugging, but in everyday use it does not show up so (once most Git
> users have this patch) we can turn on new optional extensions right
> away without alarming people.

That argument ignores the "let the users know they are using a stale
version when they did use (either by accident or deliberately) a
more recent one" value, though.

Even if we consider that this is only for debugging, I am not sure
if tracing is the right place to add.  As long as the "optional
extensions can be ignored without affecting the correctness" rule
holds, there is nothing gained by letting these messages shown for
debugging purposes, and if there is such a bug (e.g. we introduced
an optional extension but the code that wrote an index with an
optional extension wrote the non-optional part in such a way that it
cannot be correctly handled without the extension that is supposed
to be optional) we'd probably want to let users notice without
having to explicitly go into a debugging session.  If Googling for
"ignoring FNCY ext" gives "discard your index with 'reset HEAD',
because an index file with FNCY ext cannot be read without
understanding it", that may prevent damages from happening in the
first place.  On the other hand, hiding it behind tracing would mean
the user first need to exprience an unknown breakage first and then
has to enable tracing among other 47 different things to diagnose
and drill down to the root cause.