overlay, ci-automation: Another attempt at providing OEMID info

Please read the comment at the top of the coreos-base/common-oem-files
ebuild for details.

ci-automation/image_changes.sh

@@ -210,9 +210,15 @@ function get_oem_id_list() {
     arch=${1}; shift
     list_var_name=${1}; shift
 
+    local -a ebuilds=("${scripts_repo}/sdk_container/src/third_party/coreos-overlay/coreos-base/common-oem-files/common-oem-files-"*'.ebuild')
+    if [[ ${#ebuilds[@]} -eq 0 ]] || [[ ! -e ${ebuilds[0]} ]]; then
+        echo "No coreos-base/common-oem-files ebuilds?!" >&2
+        exit 1
+    fi
+
     # This defines COMMON_OEMIDS, AMD64_ONLY_OEMIDS, ARM64_ONLY_OEMIDS
     # and OEMIDS variable. We don't use the last one.
-    source "${scripts_repo}/sdk_container/src/third_party/coreos-overlay/coreos-base/common-oem-files/files/oemids.sh" local
+    source "${ebuilds[0]}" flatcar-local-variables
 
     local -n arch_oemids_ref="${arch^^}_ONLY_OEMIDS"
     local all_oemids=(

sdk_container/src/third_party/coreos-overlay/coreos-base/common-oem-files/common-oem-files-0-r4.ebuild

@@ -1,10 +1,64 @@
 # Copyright (c) 2023 The Flatcar Maintainers.
 # Distributed under the terms of the GNU General Public License v2
 
-EAPI=8
+# This is a terrible hack done in order to avoid excessive duplication
+# of OEM IDs around the place. This ebuild basically serves as a
+# Gentoo ebuild (duh…) and as a bash file to be sourced in order to
+# get arch-specific information about possible OEM IDs. The latter
+# role is assumed when the ebuild is sourced with first argument being
+# 'flatcar-local-variables'. This role is used by our image-changes
+# job. All this fluff needs to happen before we define or invoke any
+# Gentoo-specific variables or functions like "EAPI" or "inherit" that
+# may mess up sourcing.
+#
+# This can't be done with a separate shell file in FILESDIR (I tried),
+# because portage moves the ebuild into some temporary directory where
+# FILESDIR, although defined, does not even exist. Probably a security
+# measure or something. So this needs to be done as
+# all-in-terrible-one (as opposed to all-in-wonder-one).
 
-# This defines the OEMIDS variable.
-source "${FILESDIR}/oemids.sh" only-oemids
+##
+## BEGIN HACK
+##
+
+if [[ ${1:-} = 'flatcar-local-variables' ]]; then
+    local -a COMMON_OEMIDS ARM64_ONLY_OEMIDS AMD64_ONLY_OEMIDS OEMIDS
+fi
+
+COMMON_OEMIDS=(
+    ami
+    azure
+    openstack
+    packet
+    qemu
+)
+
+ARM64_ONLY_OEMIDS=(
+)
+
+AMD64_ONLY_OEMIDS=(
+    digitalocean
+    vmware
+)
+
+OEMIDS=(
+    "${COMMON_OEMIDS[@]}"
+    "${ARM64_ONLY_OEMIDS[@]}"
+    "${AMD64_ONLY_OEMIDS[@]}"
+)
+
+if [[ ${1:-} = 'flatcar-local-variables' ]]; then
+    # Leave the sourced script here.
+    return 0
+else
+    unset COMMON_OEMIDS ARM64_ONLY_OEMIDS AMD64_ONLY_OEMIDS
+fi
+
+##
+## END HACK
+##
+
+EAPI=8
 
 DESCRIPTION='Common OEM files'
 HOMEPAGE='https://www.flatcar.org/'

sdk_container/src/third_party/coreos-overlay/coreos-base/common-oem-files/files/oemids.sh

@@ -1,30 +0,0 @@
-if [[ ${1:-} = 'local' ]]; then
-    local -a COMMON_OEMIDS ARM64_ONLY_OEMIDS AMD64_ONLY_OEMIDS OEMIDS
-    shift
-fi
-
-COMMON_OEMIDS=(
-    ami
-    azure
-    openstack
-    packet
-    qemu
-)
-
-ARM64_ONLY_OEMIDS=(
-)
-
-AMD64_ONLY_OEMIDS=(
-    digitalocean
-    vmware
-)
-
-OEMIDS=(
-    "${COMMON_OEMIDS[@]}"
-    "${ARM64_ONLY_OEMIDS[@]}"
-    "${AMD64_ONLY_OEMIDS[@]}"
-)
-
-if [[ ${1:-} = 'only-oemids' ]]; then
-    unset COMMON_OEMIDS ARM64_ONLY_OEMIDS AMD64_ONLY_OEMIDS
-fi