generators: define custom main func definer and use it where applicable

There should be no functional difference, except that the error message
is changd from "three or no arguments" to "zero or three arguments". Somehow
the inverted form always seemed strange.

umask() call is also dropped from run-generator. I think it wasn't dropped in
053254e3cb because the run generator was merged
around the same time.

src/debug-generator/debug-generator.c

@@ -2,7 +2,6 @@
 
 #include "alloc-util.h"
 #include "generator.h"
-#include "main-func.h"
 #include "mkdir.h"
 #include "parse-util.h"
 #include "proc-cmdline.h"
@@ -12,8 +11,8 @@
 #include "unit-name.h"
 #include "util.h"
 
+static const char *arg_dest = NULL;
 static char *arg_default_unit = NULL;
-static const char *arg_dest = "/tmp";
 static char **arg_mask = NULL;
 static char **arg_wants = NULL;
 static bool arg_debug_shell = false;
@@ -142,17 +141,10 @@ static int generate_wants_symlinks(void) {
         return r;
 }
 
-static int run(int argc, char *argv[]) {
+static int run(const char *dest, const char *dest_early, const char *dest_late) {
         int r, q;
 
-        log_setup_generator();
-
-        if (argc > 1 && argc != 4)
-                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
-                                       "This program takes three or no arguments.");
-
-        if (argc > 1)
-                arg_dest = argv[2];
+        assert_se(arg_dest = dest_early);
 
         r = proc_cmdline_parse(parse_proc_cmdline_item, NULL, PROC_CMDLINE_RD_STRICT | PROC_CMDLINE_STRIP_RD_PREFIX);
         if (r < 0)
@@ -170,4 +162,4 @@ static int run(int argc, char *argv[]) {
         return r < 0 ? r : q;
 }
 
-DEFINE_MAIN_FUNCTION(run);
+DEFINE_MAIN_GENERATOR_FUNCTION(run);