Re: [RFC PATCH] usage: add trace2 entry upon warning()

> Emit a trace2 error event whenever warning() is called, just like when
> die(), error(), or usage() is called.
> 
> This helps debugging issues that would trigger warnings but not errors.
> In particular, this might have helped debugging an issue I encountered
> with commit graphs at $DAYJOB [1].
> 
> There is a tradeoff between including potentially relevant messages and
> cluttering up the trace output produced. I think that warning() messages
> should be included in traces, because by its nature, Git is used over
> multiple invocations of the Git tool, and a failure (currently traced)
> in a Git invocation might be caused by an unexpected interaction in a
> previous Git invocation that only has a warning (currently untraced) as
> a symptom - as is the case in [1].
> 
> [1] https://lore.kernel.org/git/20200629220744.1054093-1-jonathantanmy@google.com/
> 
> Signed-off-by: Jonathan Tan <jonathantanmy@google.com>