daemon-util: introduce notify_reloading helper

Prompted by #31951

src/shared/daemon-util.c

@@ -4,6 +4,7 @@
 #include "fd-util.h"
 #include "log.h"
 #include "string-util.h"
+#include "time-util.h"
 
 static int notify_remove_fd_warn(const char *name) {
         int r;
@@ -74,3 +75,18 @@ int notify_push_fdf(int fd, const char *format, ...) {
 
         return notify_push_fd(fd, name);
 }
+
+int notify_reloading_full(const char *status) {
+        int r;
+
+        r = sd_notifyf(/* unset_environment = */ false,
+                       "RELOADING=1\n"
+                       "MONOTONIC_USEC=" USEC_FMT
+                       "%s%s",
+                       now(CLOCK_MONOTONIC),
+                       status ? "\nSTATUS=" : "", strempty(status));
+        if (r < 0)
+                return log_debug_errno(r, "Failed to notify service manager for reloading status: %m");
+
+        return 0;
+}

src/shared/daemon-util.h

@@ -10,7 +10,7 @@
 #define NOTIFY_READY "READY=1\n" "STATUS=Processing requests..."
 #define NOTIFY_STOPPING "STOPPING=1\n" "STATUS=Shutting down..."
 
-static inline const char *notify_start(const char *start, const char *stop) {
+static inline const char* notify_start(const char *start, const char *stop) {
         if (start)
                 (void) sd_notify(false, start);
 
@@ -26,3 +26,8 @@ static inline void notify_on_cleanup(const char **p) {
 int notify_remove_fd_warnf(const char *format, ...) _printf_(1, 2);
 int close_and_notify_warn(int fd, const char *name);
 int notify_push_fdf(int fd, const char *format, ...) _printf_(2, 3);
+
+int notify_reloading_full(const char *status);
+static inline int notify_reloading(void) {
+        return notify_reloading_full("Reloading configuration...");
+}