Encode CHANNEL specification in the UC20 model names.

debian/changelog

@@ -1,6 +1,7 @@
 livecd-rootfs (2.641) UNRELEASED; urgency=medium
 
   * Configure a better nocloud datasource for subiquity cloud-init.
+  * Encode CHANNEL specification in the UC20 model names.
 
  -- Dimitri John Ledkov <xnox@ubuntu.com>  Fri, 07 Feb 2020 22:11:26 +0000
 

live-build/auto/config

@@ -365,10 +365,21 @@ case $IMAGEFORMAT in
 					;;
 				*)
 					# Ubuntu Core 20
-					# XXX: Currently uc20 assertions do not support global
+					# Currently uc20 assertions do not support global
-					#  channel overrides.
+					# channel overrides, instead we have per-channel models
+					case $CHANNEL in
+						stable)
 							MODEL="ubuntu-core-20-${MODEL#pc-}"
 							;;
+						candidate|beta|edge|dangerous)
+							MODEL="ubuntu-core-20-${MODEL#pc-}-${CHANNEL}"
+							;;
+						*)
+							echo "Unknown CHANNEL ${CHANNEL} specification for ${SUITE}"
+							exit 1
+							;;
+					esac
+					;;
 			esac
 
 			case "$ARCH+${SUBARCH:-}" in