Attempt to determine registry service IP and port if not env var not set

If the offline registry is started without the correct environment
variable, instead of failing to start, attempt to use k8s env vars to
determine the devfile registry's service ip and port.

This is fragile and experimental, so a warning is printed.

Signed-off-by: Angel Misevski <amisevsk@redhat.com>

build/dockerfiles/entrypoint.sh

@@ -69,12 +69,15 @@ if [ -n "$PUBLIC_URL" ]; then
   echo "Updating devfiles to point at internal project zip files"
   PUBLIC_URL=${PUBLIC_URL%/}
   sed -i "s|{{ DEVFILE_REGISTRY_URL }}|${PUBLIC_URL}|" "${devfiles[@]}"
-else 
+else
   if grep -q '{{ DEVFILE_REGISTRY_URL }}' "${devfiles[@]}"; then
-    echo "This devfile registry was built for offline usage and will only function" \
-         "with environment variable 'PUBLIC_URL' set to the devfile registry's" \
-         "endpoint." >> /dev/stderr
-    exit 1
+    echo "WARNING: environment variable 'CHE_DEVFILE_HTTPS_ENDPOINT' not configured" \
+         "for an offline build of this registry. This may cause issues with importing" \
+         "projects in a workspace."
+    # Experimental workaround -- detect service IP for che-devfile-registry
+    # Depends on service used being named 'che-devfile-registry'
+    URL="http://${CHE_DEVFILE_REGISTRY_SERVICE_HOST}:${CHE_DEVFILE_REGISTRY_SERVICE_PORT}"
+    sed -i "s|{{ DEVFILE_REGISTRY_URL }}|${URL}|" "${devfiles[@]}"
   fi
 fi