Re: [Mingw-cross-env-list] Improve dependency metadata specification

[Tony Theodore]

Hi Boris,


> On 7 Dec 2017, at 22:37, Nagaev Boris <address@hidden> wrote:
> 
> Can you elaborate on "optional order-only deps which won't trigger
> rebuilds", please? If A order-only depends on B, what the following
> commands do?
> 
> 1. Just building A.
> $ make A

This will build B before A

> 2. Building A, then modifying B, then building A again:
> $ make A
> $ touch src/B.mk
> $ make A

This will rebuild B but not A.

Order-only deps[1] are useful for build tools like cmake and pkgconf, changes
to these should not trigger rebuilds in the packages that use them, only
library deps should cause a rebuild.

Updates to these packages will be tested against the entire set of packages
and if a user pulls those updates and there are no changed libraries in the
subset of packages they are building, then no rebuilding is required. If the 
libraries have changed, then they will be rebuilt as normal with the newer 
versions of tools.

Hope that makes sense.

Cheers,

Tony


[1] https://www.gnu.org/software/make/manual/make.html#Prerequisite-Types