basic: when parsing verb command lines, optionally shortcut them in chroot() environments

This adds some basic infrastructure in order to fix #2015.

src/basic/verbs.c

@@ -28,6 +28,7 @@
 #include "macro.h"
 #include "string-util.h"
 #include "verbs.h"
+#include "virt.h"
 
 int dispatch_verb(int argc, char *argv[], const Verb verbs[], void *userdata) {
         const Verb *verb;
@@ -84,6 +85,11 @@ int dispatch_verb(int argc, char *argv[], const Verb verbs[], void *userdata) {
                 return -EINVAL;
         }
 
+        if ((verb->flags & VERB_NOCHROOT) && running_in_chroot() > 0) {
+                log_info("Running in chroot, ignoring request.");
+                return 0;
+        }
+
         if (name)
                 return verb->dispatch(left, argv + optind, userdata);
         else {

src/basic/verbs.h

@@ -22,7 +22,8 @@
 ***/
 
 #define VERB_ANY ((unsigned) -1)
-#define VERB_DEFAULT 1
+#define VERB_DEFAULT 1U
+#define VERB_NOCHROOT 2U
 
 typedef struct {
         const char *verb;