restructure the script

build.sh

@@ -2,16 +2,25 @@
 
 set -Eeuo pipefail
 
+# Compute podman command line arguments
+declare -a PODMAN_ARGS=()
+
+# Inject the desired CentOS Stream version as build arguments
 declare CENTOS_VERSION="10"
+PODMAN_ARGS+=( --arg CENTOS_VERSION="${CENTOS_VERSION}" --arg EPEL_VERSION="${CENTOS_VERSION}" )
+
+# Tag the resulting image with the current date
 declare TS="$(date -I)"
-declare -a PODMAN_ARGS=()
+PODMAN_ARGS+=( -t "localhost/mirrors/centos-stream-${CENTOS_VERSION}:${TS}" )
 
 # Run rsync on the previous dataset if available, to speed up transfer and save on storage.
 if podman image inspect "localhost/mirrors/centos-stream-${CENTOS_VERSION}:latest" &>/dev/null; then
   PODMAN_ARGS+=( --from "localhost/mirrors/centos-stream-${CENTOS_VERSION}:latest" )
 fi
 
-podman build -t "localhost/mirrors/centos-stream-${CENTOS_VERSION}:${TS}" "${PODMAN_ARGS[@]}" .
+# Build the image.
+# Note: during the build, the repositories will be synced and the result will be stored in the image.
+podman build "${PODMAN_ARGS[@]}" .
 podman tag "localhost/mirrors/centos-stream-${CENTOS_VERSION}:${TS}" "localhost/mirrors/centos-stream-${CENTOS_VERSION}:latest"
 
 # Here you can add the "podman push" command to send the mirror to your registry.