sh: Forget all cached command locations on any PATH change.

POSIX requires this and it is simpler than the previous code that remembered
command locations when appending directories to PATH.

In particular,
  PATH=$PATH
is no longer a no-op but discards all cached command locations.

bin/sh/exec.c

@@ -494,30 +494,7 @@ hashcd(void)
 void
 changepath(const char *newval)
 {
-	const char *old, *new;
-	int idx;
-	int firstchange;
-
-	old = pathval();
-	new = newval;
-	firstchange = 9999;	/* assume no change */
-	idx = 0;
-	for (;;) {
-		if (*old != *new) {
-			firstchange = idx;
-			if ((*old == '\0' && *new == ':')
-			 || (*old == ':' && *new == '\0'))
-				firstchange++;
-			old = new;	/* ignore subsequent differences */
-		}
-		if (*new == '\0')
-			break;
-		if (*new == ':') {
-			idx++;
-		}
-		new++, old++;
-	}
-	clearcmdentry(firstchange);
+	clearcmdentry(0);
 }
 
 

tools/regression/bin/sh/execution/hash1.0

@@ -0,0 +1,12 @@
+# $FreeBSD$
+
+T=`mktemp -d "${TMPDIR:-/tmp}/sh-test.XXXXXXXX"` || exit
+trap 'rm -rf "${T}"' 0
+PATH=$T:$PATH
+ls -ld . >/dev/null
+cat <<EOF >"$T/ls"
+:
+EOF
+chmod 755 "$T/ls"
+PATH=$PATH
+ls -ld .