[yocto] CONFFILES journey form source dir to rootfs

[Alan Martinovic]

Hi,
I'm trying to understand how a conf file finds its way from source to
the rootfs.

The example is use is `journald.conf` from systemd.
The file originates from systemd source:
    work/cortexa7hf-neon-vfpv4-senic-linux-gnueabi/systemd/1_234-r0/git/src/journal/journald.conf

In the environment is only mentioned as a part of the CONFFILES.
[output of `bitbake systemd -e` formated for readability]:

    # $CONFFILES [2 operations]
    #   set /mnt/data/alan/work/senic-os/oe/meta/conf/documentation.conf:116
    #     [doc] "Identifies editable or configurable files that are
part of a package."
    #   override[systemd]:rename from CONFFILES_${PN} data.py:116 [expandKeys]
    #     "${sysconfdir}/machine-id
           ${sysconfdir}/systemd/coredump.conf
           ${sysconfdir}/systemd/journald.conf
           ${sysconfdir}/systemd/logind.conf
           ${sysconfdir}/systemd/system.conf
           ${sysconfdir}/systemd/user.conf"
    # pre-expansion value:
    #   "None"
    #
    # $CONFFILES_systemd
    #   rename from CONFFILES_${PN} data.py:116 [expandKeys]
    #     "${sysconfdir}/machine-id
           ${sysconfdir}/systemd/coredump.conf
           ${sysconfdir}/systemd/journald.conf
           ${sysconfdir}/systemd/logind.conf
           ${sysconfdir}/systemd/system.conf
           ${sysconfdir}/systemd/user.conf"
    CONFFILES_systemd="/etc/machine-id
            /etc/systemd/coredump.conf
            /etc/systemd/journald.conf
            /etc/systemd/logind.conf
            /etc/systemd/system.conf
            /etc/systemd/user.conf"


The file successfully ends up at `/etc/systemd/journald.conf`.

Why isn't there an action in the environment showing the copying of
journald.conf
from `...git/src/journal/journald.conf` to
`${sysconfdir}/systemd/journald.conf`?


Disclaimer:
There were also some sed related actions with the file in the environment
which I dropped to reduce noise.

Be Well,
Alan