Improve parsing of local mkosi config

[septatrix]

Clarify that mkosi.local shall be a directory with a mkosi.conf file inside of it.

[septatrix]

I think the cleaner fix is to also unconditionally parse mkosi.local/ iff it is a dir to allow stuff like mkosi.local/mkosi.conf.d/... without requiring a mkosi.conf file for detection

[septatrix]

To expand on the "and allows working around some limitations of the config system", the problem is when one wants to locally include something which uses matches or profiles that are set by mkosi.conf.

# File: mkosi.conf
[Distribution]
Distribution=arch

# File: mkosi.local/mkosi.conf.d/20-include-tools.conf
[Include]
Include=mkosi-tools

This can now be worked around by putting the distro configuration at mkosi.local/mkosi.conf.d/10-default-distro.conf and ensuring that this file is tracked by git. Not a very pretty solution but it enables a few things that are otherwise not possible. Every other solution (e.g. postpone parsing of configs with [Matches]) I could think of had other disadvantages or just moves that problem to other scenarios

[behrmann]

Sorry, late to the game, the "this file or directory" makes sense logically, but should probably be an "and", since above we now say that both are parsed. In the last line it should it should also read "are" instead of "is", since both are intended for local configuration.

[septatrix]

-> #3581