dissect: show intended architecture of a disk image

We already determine the architecture of disk images and make a choice,
and store it per partition. Let's make this accessible globally.

src/dissect/dissect.c

@@ -603,6 +603,9 @@ static int action_dissect(DissectedImage *m, LoopDevice *d) {
 
         printf(" Sec. Size: %" PRIu32 "\n", m->sector_size);
 
+        printf("     Arch.: %s\n",
+               strna(architecture_to_string(dissected_image_architecture(m))));
+
         if (arg_json_format_flags & JSON_FORMAT_OFF)
                 putc('\n', stdout);
 

src/shared/dissect-image.c

@@ -3156,6 +3156,20 @@ finish:
         return r;
 }
 
+Architecture dissected_image_architecture(DissectedImage *img) {
+        assert(img);
+
+        if (img->partitions[PARTITION_ROOT].found &&
+            img->partitions[PARTITION_ROOT].architecture >= 0)
+                return img->partitions[PARTITION_ROOT].architecture;
+
+        if (img->partitions[PARTITION_USR].found &&
+            img->partitions[PARTITION_USR].architecture >= 0)
+                return img->partitions[PARTITION_USR].architecture;
+
+        return _ARCHITECTURE_INVALID;
+}
+
 int dissect_loop_device(
                 LoopDevice *loop,
                 const VeritySettings *verity,

src/shared/dissect-image.h

@@ -160,6 +160,8 @@ int dissected_image_mount_and_warn(DissectedImage *m, const char *where, uid_t u
 
 int dissected_image_acquire_metadata(DissectedImage *m, DissectImageFlags extra_flags);
 
+Architecture dissected_image_architecture(DissectedImage *m);
+
 DecryptedImage* decrypted_image_ref(DecryptedImage *p);
 DecryptedImage* decrypted_image_unref(DecryptedImage *p);
 DEFINE_TRIVIAL_CLEANUP_FUNC(DecryptedImage*, decrypted_image_unref);