[gentoo-dev] Questions on overlays, repositories and PMS

[Michael Lienhardt]

I started refactoring my solver to make it more modular, to fix some details w.r.t. the PMS and to manage different repositories.
I thus have several questions on how multiple repositories work in portage.

1. My understanding was that /etc/portage/repos.conf replaced the PORTDIR_OVERLAY variable, however this variable is still documented (e.g. in https://devmanual.gentoo.org/general-concepts/overlay/index.html).
Was my intuition right?
Or in other word, it is enough to only look at /etc/portage/repos.conf?
In general, an overlay is a repository, i.e., a valid tree layout for the PMS, right (as stated in https://devmanual.gentoo.org/general-concepts/overlay/index.html)?

2. the PMS states that any valid repository has a profiles folder which can contain profiles and a package.mask file.
  - can the profiles in a repository different from DEFAULT be selected?
  - is the package.mask file apply only on the packages of that repository, or on every packages of every repositories listed in /etc/portage/repos.conf?

3. many repositories do not have an eclass folder, and miss many (optional) configuration files in the profiles folder (like arch.list, categories):
  - is such information implicitly inherited from the DEFAULT repository (even though https://wiki.gentoo.org/wiki//etc/portage/repos.conf states that it is not)?
      the brother overlay (https://github.com/stefan-langenmaier/brother-overlay) does not specify any masters
  - when the eclass folder, profiles/arch.list and such are present, is the data from the DEFAULT repository still implicitly inherited?
  - when the eclass folder, profiles/arch.list and such are present, are they visible globally (i.e., a package from another repository can use a keyword of the arch.list and inherit from one of the eclass)?

4. is the "masters" attribute in /etc/portage/repos.conf make the repository inherit other data than the eclasses?

5. since every repos can have a profiles/categories file, is the file /etc/portage/categories obsolete (or should it be)?


Best Regards,
Michael Lienhardt