pretty-print: add format-string version of draw_progress_bar()

We often format the prefix string via asprintf() before, let's hence add
a helper for that.

src/shared/pretty-print.c

@@ -548,6 +548,22 @@ void draw_progress_bar(const char *prefix, double percentage) {
         draw_progress_bar_unbuffered(prefix, percentage);
 }
 
+int draw_progress_barf(double percentage, const char *prefixf, ...) {
+        _cleanup_free_ char *s = NULL;
+        va_list ap;
+        int r;
+
+        va_start(ap, prefixf);
+        r = vasprintf(&s, prefixf, ap);
+        va_end(ap);
+
+        if (r < 0)
+                return -ENOMEM;
+
+        draw_progress_bar(s, percentage);
+        return 0;
+}
+
 void clear_progress_bar(const char *prefix) {
         WITH_BUFFERED_STDERR;
         clear_progress_bar_unbuffered(prefix);

src/shared/pretty-print.h

@@ -54,6 +54,7 @@ int terminal_tint_color(double hue, char **ret);
 bool shall_tint_background(void);
 
 void draw_progress_bar(const char *prefix, double percentage);
+int draw_progress_barf(double percentage, const char *prefixf, ...) _printf_(2, 3);
 void clear_progress_bar(const char *prefix);
 void draw_progress_bar_unbuffered(const char *prefix, double percentage);
 void clear_progress_bar_unbuffered(const char *prefix);