Restore old semantics of "netdata -W set" command (#8987)

claim/README.md

@@ -121,7 +121,7 @@ docker run -d --name=netdata \
   --cap-add SYS_PTRACE \
   --security-opt apparmor=unconfined \
   netdata/netdata \
-  /usr/sbin/netdata -D -W set cloud global enabled true -W set cloud global "cloud base url" "https://app.netdata.cloud" -W "claim -token=TOKEN -rooms=ROOM1,ROOM2 -url=https://app.netdata.cloud"
+  /usr/sbin/netdata -D -W set2 cloud global enabled true -W set2 cloud global "cloud base url" "https://app.netdata.cloud" -W "claim -token=TOKEN -rooms=ROOM1,ROOM2 -url=https://app.netdata.cloud"
 ```
 
 The container runs in detached mode, so you won't see any output. If the node does not appear in your Space, you can run

daemon/main.c

@@ -1086,6 +1086,36 @@ int main(int argc, char **argv) {
                             debug_flags = strtoull(optarg, NULL, 0);
                         }
                         else if(strcmp(optarg, "set") == 0) {
+                            if(optind + 3 > argc) {
+                                fprintf(stderr, "%s", "\nUSAGE: -W set 'section' 'key' 'value'\n\n"
+                                        " Overwrites settings of netdata.conf.\n"
+                                        "\n"
+                                        " These options interact with: -c netdata.conf\n"
+                                        " If -c netdata.conf is given on the command line,\n"
+                                        " before -W set... the user may overwrite command\n"
+                                        " line parameters at netdata.conf\n"
+                                        " If -c netdata.conf is given after (or missing)\n"
+                                        " -W set... the user cannot overwrite the command line\n"
+                                        " parameters."
+                                        "\n"
+                                );
+                                return 1;
+                            }
+                            const char *section = argv[optind];
+                            const char *key = argv[optind + 1];
+                            const char *value = argv[optind + 2];
+                            optind += 3;
+
+                            // set this one as the default
+                            // only if it is not already set in the config file
+                            // so the caller can use -c netdata.conf before or
+                            // after this parameter to prevent or allow overwriting
+                            // variables at netdata.conf
+                            config_set_default(section, key,  value);
+
+                            // fprintf(stderr, "SET section '%s', key '%s', value '%s'\n", section, key, value);
+                        }
+                        else if(strcmp(optarg, "set2") == 0) {
                             if(optind + 4 > argc) {
                                 fprintf(stderr, "%s", "\nUSAGE: -W set 'conf_file' 'section' 'key' 'value'\n\n"
                                         " Overwrites settings of netdata.conf or cloud.conf\n"