Re: [PATCH 1/3] wincred: ignore unknown lines (do not die)

> > It is the expectation that credential helpers be liberal in what they
> > accept and conservative in what they return, to allow for future growth
> > and evolution of the protocol/interaction.
> 
> That is nice in principle, and the updated code below may work well
> with existing "other side of the connection" (codepaths in "git"
> that asks credential API to talk to the helpers), but I am not sure
> if this is always a safe thing to do.
> 
> When we gain a new "command" in the protocol, if we just read it
> without understanding it, would we open ourselves to a risk of
> breaking the protocol communication, worst of which may be to
> deadlock?  A new command, when received by a more recent helper that
> understands how to react to it, may _require_ it to write more than
> "username" and "password" back to "git" from get_credential(), for
> example, but the helper with this patch alone, while not complaining
> about seeing such a new and unknown command, would not know how to
> compute and write that third thing other than "username" and
> "password"---would the other side who issued that new command get
> stuck waiting for us to return the third thing?  Worse yet, the new
> command may expect us to read further in get_credential()
> (e.g. maybe they will give us a challenge, which may need to be used
> when yielding the "username" and "password" things), but because we
> do not even know we need to read, their attempt to write to us may
> get them stuck, and that is when we are expecting to write to them,
> easily leading to a deadlock, no?