[Buildroot] [PATCH] infra: add the transient download mechanism

[Yann E. MORIN <yann.morin.1998@free.fr>]

Thomas, All,

On 2020-01-16 11:05 +0100, Thomas Petazzoni spake thusly:
> On Thu, 16 Jan 2020 10:01:09 +0000
> Nicolas Carrier <nicolas.carrier@orolia.com> wrote:
> 
> > Just to be sure I understand, when you say "when TRANSIENT_DOWNLOAD is
> > NO.", it'd be the same as if TRANSIENT_DOWNLOAD download is not defined
> > at all, right?
> 
> Yes.
> 
> There is maybe a little bit of an issue in Yann's current
> implementation as he does:
> 
> 	$(if $($(2)_DOWNLOAD_TRANSIENT),-F) \
> 
> so in fact, -F would be passed as soon as <pkg>_DOWNLOAD_TRANSIENT is
> non-empty, so <pkg>_DOWNLOAD_TRANSIENT = NO would in fact pass -F.
> 
> But this bug already exists for <pkg>_GIT_SUBMODULES:
> 
> 	$(if $($(2)_GIT_SUBMODULES),-r) \

Yeah, I just mirrored for transient wghat we already had for git
submodules.

> And it is trivial to fix.

If ever needed...

    $(if $(filter YES,$($(2)_DOWNLOAD_TRANSIENT)),-F)

(note that there is no equality test in GNU make, but there is one
simple one described in GMSL).

> > If it's the case, then that seems to me like a good idea, because it
> > renders explicit the risk taken by the user when using a branch (which
> > can be done unknowingly ATM).

Yup.

Regards,
Yann E. MORIN.

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