Re: [BuildStream] Proposal: Decouple source tracking and building

[tristan maat codethink co uk (Tristan Daniël Maat)]

Hi,

> Hi all,
>
> tl;dr: Remove `--track-*` options from `bst build` and simplify codebase.

I'd really like to see this gone, too, it would simplify a number of
things :)

The recent UI proposals also marked this as the only thing we never do
implicitly, so I don't believe it's unreasonable to ask a user to run
a separate command to do this.

> `bst source track` followed by `bst build`. Can people think of any other use
> cases that would be negatively affected by this change, other than having to
> type two commands instead of one?

While I agree with the thought in general, I don't think the "having
to type two commands" issue should just be dismissed. The reason James
and I did not suggest this change was precisely that - by running it
as two commands, we miss out on parallelism when tracking a large
system.

This might seem like it doesn't matter at first glance (because large
projects will probably manually track source versions anyway), but I
think it might be a problem for small projects that depend on large
junctions, since the majority of their build time can be waiting for
BuildStream to figure out whether all their junctions are up-to-date.

In practice I think that might be rare enough of a situation that we
can stop supporting it, but I wouldn't want to just dismiss the
thought.

> Thanks!
> Chandan

Thanks for raising this :)

Tristan