[PATCH setup] add --build-depend option

[Jon Turney]

On 17/07/2025 00:31, John Haugabook via Cygwin-apps wrote:
> Hello,
> 
> This patch adds an option --build-depend that, when called; installs the
> packages listed in the build-depends property of setup.ini. It is for
> someone who wants to build the binaries of a package themselves, enabling
> them to pass one stringed package in lieu of a vector of packages.

Thanks very much for looking at this!

> Right now this is more or less a rough draft as feedback requested i.e.
> what's the best way to implement this, and to get specific detailed
> hand-holding help on two things (unless better approach):
>   1. Using the correct setup.ini file (debugged using copy of setup.ini) and
>      passing it as a string to the "stream" parameter of build_depend(), which
>      is declared as:
>      - std::string build_depend(std::string pkg_search, std::string stream)
>      in build_depends.h.

So, I'd suggest that's not quite the right approach, as it falls down 
when setup is requested to read from multiple package repositories.

(e.g. when fetching a supplemental set of packages from an overlay 
server, as described in [1])

[1] https://cygwin.com/package-server.html

If you take a look at 
IniDBBuilderPackage.cc:IniDBBuilderPackage::buildBeginBuildDepends(), 
you'll see where the current handling of build-requires data parsed from 
setup.ini stops.

It should be relatively straightforward to add another "nodeList" here, 
to assemble the data parsed from build-requires: lines in setup.ini
(identically to the existing handling of 
depends/obsoletes/provides/conflicts)

[There's a bit here where I skip over plumbing the build-requires into 
the packagedb]

> 
>   2. Convert and handle successful output of build_depend(), passing it to
>      "PackageOption" in package_meta.cc (unless better way) as a vector as
>      if the output from build_depend() was passed to -P, --packages.


In choose.cc:ChooserPage::applyCommandLinePackageSelection() there's an 
existing block of code which handles, uh, command line package selection.

It seems like we could have a separate chunk here, which iterates over 
the package names supplied to the '--build-depends' option, fetches 
their build-requires, and marks those packages as "to be installed".