id128: add new "-u" switch for outputting Ids in UUID format

For some unrelated stuff I wanted the machine ID in UUID format, and it
was annoying doing that manually. So let's add a switch for this, so
that this works:

    systemd-id128 machine-id -u

src/shared/id128-print.c

@@ -10,15 +10,22 @@
 #include "pretty-print.h"
 #include "terminal-util.h"
 
-int id128_pretty_print(sd_id128_t id, bool pretty) {
-        unsigned i;
+int id128_pretty_print(sd_id128_t id, Id128PrettyPrintMode mode) {
         _cleanup_free_ char *man_link = NULL, *mod_link = NULL;
         const char *on, *off;
+        unsigned i;
 
-        if (!pretty) {
+        assert(mode >= 0);
+        assert(mode < _ID128_PRETTY_PRINT_MODE_MAX);
+
+        if (mode == ID128_PRINT_ID128) {
                 printf(SD_ID128_FORMAT_STR "\n",
                        SD_ID128_FORMAT_VAL(id));
                 return 0;
+        } else if (mode == ID128_PRINT_UUID) {
+                printf(SD_ID128_UUID_FORMAT_STR "\n",
+                       SD_ID128_FORMAT_VAL(id));
+                return 0;
         }
 
         on = ansi_highlight();
@@ -53,7 +60,7 @@ int id128_pretty_print(sd_id128_t id, bool pretty) {
         return 0;
 }
 
-int id128_print_new(bool pretty) {
+int id128_print_new(Id128PrettyPrintMode mode) {
         sd_id128_t id;
         int r;
 
@@ -61,5 +68,5 @@ int id128_print_new(bool pretty) {
         if (r < 0)
                 return log_error_errno(r, "Failed to generate ID: %m");
 
-        return id128_pretty_print(id, pretty);
+        return id128_pretty_print(id, mode);
 }

src/shared/id128-print.h

@@ -6,5 +6,13 @@
 
 #include "sd-id128.h"
 
-int id128_pretty_print(sd_id128_t id, bool pretty);
-int id128_print_new(bool pretty);
+typedef enum Id128PrettyPrintMode {
+        ID128_PRINT_ID128,
+        ID128_PRINT_UUID,
+        ID128_PRINT_PRETTY,
+        _ID128_PRETTY_PRINT_MODE_MAX,
+        _ID128_PRETTY_PRINT_MODE_INVALID = -1
+} Id128PrettyPrintMode;
+
+int id128_pretty_print(sd_id128_t id, Id128PrettyPrintMode mode);
+int id128_print_new(Id128PrettyPrintMode mode);