udev/builtin: introduce udev_builtin_import_property() helper function

This is not used in this commit, but will be used later commits.

src/udev/udev-builtin.c

@@ -154,3 +154,26 @@ int udev_builtin_add_propertyf(sd_device *dev, bool test, const char *key, const
 
         return udev_builtin_add_property(dev, test, key, val);
 }
+
+int udev_builtin_import_property(sd_device *dev, sd_device *src, bool test, const char *key) {
+        const char *val;
+        int r;
+
+        assert(dev);
+        assert(key);
+
+        if (!src)
+                return 0;
+
+        r = sd_device_get_property_value(src, key, &val);
+        if (r == -ENOENT)
+                return 0;
+        if (r < 0)
+                return log_device_debug_errno(src, r, "Failed to get property \"%s\", ignoring: %m", key);
+
+        r = udev_builtin_add_property(dev, test, key, val);
+        if (r < 0)
+                return r;
+
+        return 1;
+}

src/udev/udev-builtin.h

@@ -84,5 +84,6 @@ void udev_builtin_list(void);
 bool udev_builtin_should_reload(void);
 int udev_builtin_add_property(sd_device *dev, bool test, const char *key, const char *val);
 int udev_builtin_add_propertyf(sd_device *dev, bool test, const char *key, const char *valf, ...) _printf_(4, 5);
+int udev_builtin_import_property(sd_device *dev, sd_device *src, bool test, const char *key);
 int udev_builtin_hwdb_lookup(sd_device *dev, const char *prefix, const char *modalias,
                              const char *filter, bool test);