Do not use arg.h for tools which take no flags

We've already seen the issue with echo(1): Before we changed it to
ignore "--", the command

$ echo --

did not work as expected. Given POSIX mandated this and makes most
sense, in the interest of consistency the other tools need to be
streamlined for that as well.
Looking at yes(1) for instance, there's no reason to skip "--" in
the argument list.
We do not have long options like GNU does and there's no reason to
tinker with that here.

The majority of tools changed are ones taking lists of arguments
or only a single one. There's no reason why dirname should "fail"
on "--". In the end, this is a valid name.

The practice of hand-holding the user was established with the GNU
coreutils. "--help" and "--version" long-options are a disgrace to
what could've been done properly with manpages.

basename.c

@@ -17,10 +17,7 @@ main(int argc, char *argv[])
 	ssize_t off;
 	char *p;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (argc != 1 && argc != 2)
 		usage();

chroot.c

@@ -17,10 +17,7 @@ main(int argc, char *argv[])
 	char *shell[] = { "/bin/sh", "-i", NULL }, *aux, *cmd;
 	int savederrno;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (!argc)
 		usage();

cksum.c

@@ -84,22 +84,13 @@ cksum(FILE *fp, const char *s)
 	putchar('\n');
 }
 
-static void
-usage(void)
-{
-	eprintf("usage: %s [file ...]\n", argv0);
-}
-
 int
 main(int argc, char *argv[])
 {
 	FILE *fp;
 	int ret = 0;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (!argc) {
 		cksum(stdin, NULL);

dirname.c

@@ -13,10 +13,7 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (argc != 1)
 		usage();

echo.c

@@ -8,7 +8,9 @@ main(int argc, char *argv[])
 {
 	int nflag = 0;
 
-	if (*++argv && !strcmp(*argv, "-n")) {
+	argv0 = argv[0], argc--, argv++;
+
+	if (*argv && !strcmp(*argv, "-n")) {
 		nflag = 1;
 		argc--, argv++;
 	}

hostname.c

@@ -16,10 +16,7 @@ main(int argc, char *argv[])
 {
 	char host[HOST_NAME_MAX + 1];
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (!argc) {
 		if (gethostname(host, sizeof(host)) < 0)

link.c

@@ -12,10 +12,7 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (argc != 2)
 		usage();

nohup.c

@@ -19,10 +19,7 @@ main(int argc, char *argv[])
 {
 	int fd, savederrno;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (!argc)
 		usage();

printenv.c

@@ -6,22 +6,13 @@
 
 extern char **environ;
 
-static void
-usage(void)
-{
-	eprintf("usage: %s [var ...]\n", argv0);
-}
-
 int
 main(int argc, char *argv[])
 {
 	char *var;
 	int ret = 0;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (!argc) {
 		for (; *environ; environ++)

setsid.c

@@ -15,10 +15,7 @@ main(int argc, char *argv[])
 {
 	int savederrno;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (!argc)
 		usage();

sleep.c

@@ -14,10 +14,7 @@ main(int argc, char *argv[])
 {
 	unsigned seconds;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (argc != 1)
 		usage();

sponge.c

@@ -15,10 +15,7 @@ main(int argc, char *argv[])
 {
 	FILE *fp, *tmpfp;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (argc != 1)
 		usage();

sync.c

@@ -12,10 +12,7 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (argc)
 		usage();

tty.c

@@ -15,10 +15,7 @@ main(int argc, char *argv[])
 {
 	char *tty;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (argc)
 		usage();

unlink.c

@@ -12,10 +12,7 @@ usage(void)
 int
 main(int argc, char *argv[])
 {
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	if (argc != 1)
 		usage();

yes.c

@@ -3,21 +3,12 @@
 
 #include "util.h"
 
-static void
-usage(void)
-{
-	eprintf("usage: %s [string ...]\n", argv0);
-}
-
 int
 main(int argc, char *argv[])
 {
 	char **p;
 
-	ARGBEGIN {
+	argv0 = argv[0], argc--, argv++;
-	default:
-		usage();
-	} ARGEND;
 
 	for (p = argv; ; p = (*p && *(p + 1)) ? p + 1 : argv) {
 		fputs(*p ? *p : "y", stdout);