Re: [PATCH 6/7] trace: disable key after write error

> If we get a write error writing to a trace descriptor, the
> error isn't likely to go away if we keep writing. Instead,
> you'll just get the same error over and over. E.g., try:
>
>   GIT_TRACE_PACKET=42 git ls-remote >/dev/null
>
> You don't really need to see:
>
>   warning: unable to write trace for GIT_TRACE_PACKET: Bad file descriptor
>
> hundreds of times. We could fallback to tracing to stderr,
> as we do in the error code-path for open(), but there's not
> much point. If the user fed us a bogus descriptor, they're
> probably better off fixing their invocation. And if they
> didn't, and we saw a transient error (e.g., ENOSPC writing
> to a file), it probably doesn't help anybody to have half of
> the trace in a file, and half on stderr.