Re: [PATCH 0/5] promise: introduce promises to track success or error

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

Patrick Steinhardt <ps@pks.im> writes:

> While we're already at it throwing ideas around, I also have to wonder
> whether this would be a long-term solution towards computer-friendly
> errors. One of the problems we quite frequently hit in Gitaly is that we
> are forced to parse error messages in order to figure out why exactly
> something has failed. Needless to say, this is quite fragile and also
> feels very wrong.
>
> Now if we had a more structured way to pass errors around this might
> also enable us to convey more meaning to the caller of Git commands. In
> a hypothetical world where all errors were using an explicit error type,
> then this error type could eventually become richer and contain more
> information that is relevant to the calling script. And if such rich
> error information was available, then it would not be that far fetched
> to ask Git to emit errors in a computer-parsable format like for example
> JSON.

I do not know about the "JSON-parseable" part, but a structured
error message, or even just a set of error codes that can be
recorded in an index, might already be a great improvement.