new: [compose-core] prevent sub compose command to try to solve again relation constraints

This is because sub-compose command are often in a subset of the
services and as a consequence they do not share the same environment
and might solve the constraints differently.

bin/compose

@@ -1006,6 +1006,22 @@ load_env() {
             fi
         done < "$COMPOSE_LAUNCHER_OPTS"
     fi
+    if [ -n "$ALL_RELATIONS" ]; then
+        if ! [ -e "$ALL_RELATIONS" ]; then
+            err "Variable \$ALL_RELATION provided but it doesn't point on an existing file."
+            return 1
+        fi
+        if ! [ -r "$ALL_RELATIONS" ]; then
+            err "Variable \$ALL_RELATION provided but it doesn't point on a readable file."
+            return 1
+        fi
+        NEW_ALL_RELATIONS="$COMPOSE_CACHE/${ALL_RELATIONS##*/}"
+        if [ "$NEW_ALL_RELATIONS" != "$ALL_RELATIONS" ]; then
+            cp "$ALL_RELATIONS" "$NEW_ALL_RELATIONS" || return 1
+        fi
+        docker_run_opts+=("-e" "ALL_RELATIONS=$NEW_ALL_RELATIONS")
+    fi
+
 }
 
 show_env() {
@@ -1019,6 +1035,9 @@ show_env() {
     echo "  COMPOSE_LAUNCHER_CACHE: $COMPOSE_LAUNCHER_CACHE"
     echo "  SESSION_DIR: $SESSION_DIR"
     echo "  TZ_PATH: $TZ_PATH"
+    if [ -n "$ALL_RELATIONS" ]; then
+        echo "  ALL_RELATIONS: $ALL_RELATIONS"
+    fi
 }
 
 

bin/compose-core

@@ -2548,6 +2548,11 @@ get_all_relations () {
     local cache_file="$state_tmpdir/$FUNCNAME.cache.$(H "$@" "$(declare -p without_relations)")" \
           services
 
+    if [ -n "$ALL_RELATIONS" ]; then
+        cat "$ALL_RELATIONS" || return 1
+        return 0
+    fi
+
     if [ -e "${cache_file}" ]; then
         #debug "$FUNCNAME: SESSION cache hit $1"
         export ALL_RELATIONS="$cache_file"
@@ -2899,6 +2904,11 @@ run_service_relations () {
 
             # debug "  Relations of ${DARKYELLOW}$subservice${NORMAL}:"
             while read-0 relation_name target_service relation_config tech_dep; do
+                [ "${without_relations[$service:$relation_name]}" ] && {
+                    debug "Skipping $DARKYELLOW$service$NORMAL --$DARKBLUE$relation_name$NORMAL--> $DARKYELLOW*$NORMAL"
+                    continue
+                }
+
                 export relation_config
                 export TARGET_SERVICE_NAME=$target_service
                 MASTER_TARGET_SERVICE_NAME=$(get_top_master_service_for_service "$target_service") || return 1