Add strv_prepend

Inserts a copy of the value at the head of the list.

src/basic/strv.c

@@ -537,6 +537,19 @@ int strv_consume_prepend(char ***l, char *value) {
         return r;
 }
 
+int strv_prepend(char ***l, const char *value) {
+        char *v;
+
+        if (!value)
+                return 0;
+
+        v = strdup(value);
+        if (!v)
+                return -ENOMEM;
+
+        return strv_consume_prepend(l, v);
+}
+
 int strv_extend(char ***l, const char *value) {
         char *v;