Obtained from: partly from 1.1.5

Convert "" to "." for "cd" and "cd ''".  chdir("") is required to fail
on POSIX systems.

bin/sh/cd.c

@@ -33,7 +33,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: cd.c,v 1.2 1994/09/24 02:57:24 davidg Exp $
+ *	$Id: cd.c,v 1.3 1994/11/06 01:29:26 jkh Exp $
  */
 
 #ifndef lint
@@ -88,6 +88,8 @@ cdcmd(argc, argv)  char **argv; {
 	nextopt(nullstr);
 	if ((dest = *argptr) == NULL && (dest = bltinlookup("HOME", 1)) == NULL)
 		error("HOME not set");
+	if (*dest == '\0')
+		dest = ".";
 	if (dest[0] == '-' && dest[1] == '\0') {
 		dest = prevdir ? prevdir : curdir;
 		print = 1;
@@ -220,7 +222,7 @@ docd(dest, print)
 	STPUTC('\0', p);
 	p = grabstackstr(p);
 	INTOFF;
-	if (chdir(p) < 0) {
+	if (chdir(*p ? p : ".") < 0) {
 		INTON;
 		return -1;
 	}