ash: fix "unset OPTIND" throwing an error message

Added test was failing quite severely. Now only one subtest fails
(OPTERR=0 has no effect).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash.c

@@ -2099,7 +2099,9 @@ extern struct globals_var *const ash_ptr_to_globals_var;
 static void FAST_FUNC
 getoptsreset(const char *value)
 {
-	shellparam.optind = number(value) ?: 1;
+	shellparam.optind = 1;
+	if (is_number(value))
+		shellparam.optind = number(value) ?: 1;
 	shellparam.optoff = -1;
 }
 #endif

shell/ash_test/ash-getopts/getopt_simple.right

@@ -0,0 +1,34 @@
+*** no OPTIND, optstring:'ab' args:-a -b c
+var:'a' OPTIND:2
+var:'b' OPTIND:3
+exited: rc:0 var:'?' OPTIND:3
+*** OPTIND=1, optstring:'ab' args:-a -b c
+var:'a' OPTIND:2
+var:'b' OPTIND:3
+exited: rc:0 var:'?' OPTIND:3
+*** OPTIND=0, optstring:'ab' args:-a -b c
+var:'a' OPTIND:2
+var:'b' OPTIND:3
+exited: rc:0 var:'?' OPTIND:3
+*** unset OPTIND, optstring:'ab' args:-a -b c
+var:'a' OPTIND:2
+var:'b' OPTIND:3
+exited: rc:0 var:'?' OPTIND:3
+*** optstring:'ab' args:-a -b c
+1 rc:0 var:'a' OPTIND:2
+2 rc:0 var:'b' OPTIND:3
+3 rc:1 var:'?' OPTIND:3
+*** unset OPTIND, optstring:'ab' args:-a c -c -b d
+var:'a' OPTIND:2
+exited: rc:0 var:'?' OPTIND:2
+*** unset OPTIND, optstring:'ab' args:-a -c -b d
+var:'a' OPTIND:2
+Illegal option -c
+var:'?' OPTIND:3
+var:'b' OPTIND:4
+exited: rc:0 var:'?' OPTIND:4
+*** unset OPTIND, OPTERR=0, optstring:'ab' args:-a -c -b d
+var:'a' OPTIND:2
+var:'?' OPTIND:3
+var:'b' OPTIND:4
+exited: rc:0 var:'?' OPTIND:4

shell/ash_test/ash-getopts/getopt_simple.tests

@@ -0,0 +1,75 @@
+# Simple usage cases for getopts.
+#
+# OPTIND is either not touched at all (first loop with getopts,
+# relying on shell startup init), or getopts state is reset
+# before new loop with "unset OPTIND", "OPTIND=1" or "OPTIND=0".
+#
+# Each option is a separate argument (no "-abc"). This conceptually
+# needs only $OPTIND to hold getopts state.
+#
+# We check that loop does not stop on unknown option (sets "?"),
+# stops on _first_ non-option argument.
+
+echo "*** no OPTIND, optstring:'ab' args:-a -b c"
+var=QWERTY
+while getopts "ab" var -a -b c; do
+	echo "var:'$var' OPTIND:$OPTIND"
+done
+# unfortunately, "rc:0" is shown since while's overall exitcode is "success"
+echo "exited: rc:$? var:'$var' OPTIND:$OPTIND"
+
+# Resetting behavior =1
+echo "*** OPTIND=1, optstring:'ab' args:-a -b c"
+OPTIND=1
+while getopts "ab" var -a -b c; do
+	echo "var:'$var' OPTIND:$OPTIND"
+done
+echo "exited: rc:$? var:'$var' OPTIND:$OPTIND"
+
+# Resetting behavior =0
+echo "*** OPTIND=0, optstring:'ab' args:-a -b c"
+OPTIND=0
+while getopts "ab" var -a -b c; do
+	echo "var:'$var' OPTIND:$OPTIND"
+done
+echo "exited: rc:$? var:'$var' OPTIND:$OPTIND"
+
+# Resetting behavior "unset"
+echo "*** unset OPTIND, optstring:'ab' args:-a -b c"
+unset OPTIND
+while getopts "ab" var -a -b c; do
+	echo "var:'$var' OPTIND:$OPTIND"
+done
+echo "exited: rc:$? var:'$var' OPTIND:$OPTIND"
+
+# What is the final exitcode?
+echo "*** optstring:'ab' args:-a -b c"
+unset OPTIND
+getopts "ab" var -a -b c; echo "1 rc:$? var:'$var' OPTIND:$OPTIND"
+getopts "ab" var -a -b c; echo "2 rc:$? var:'$var' OPTIND:$OPTIND"
+getopts "ab" var -a -b c; echo "3 rc:$? var:'$var' OPTIND:$OPTIND"
+
+# Where would it stop? c or -c?
+echo "*** unset OPTIND, optstring:'ab' args:-a c -c -b d"
+unset OPTIND
+while getopts "ab" var -a c -c -b d; do
+	echo "var:'$var' OPTIND:$OPTIND"
+done
+echo "exited: rc:$? var:'$var' OPTIND:$OPTIND"
+
+# What happens on unknown option?
+echo "*** unset OPTIND, optstring:'ab' args:-a -c -b d"
+unset OPTIND
+while getopts "ab" var -a -c -b d; do
+	echo "var:'$var' OPTIND:$OPTIND"
+done
+echo "exited: rc:$? var:'$var' OPTIND:$OPTIND"
+
+# ORTERR=0 suppresses error message?
+echo "*** unset OPTIND, OPTERR=0, optstring:'ab' args:-a -c -b d"
+unset OPTIND
+OPTERR=0
+while getopts "ab" var -a -c -b d; do
+	echo "var:'$var' OPTIND:$OPTIND"
+done
+echo "exited: rc:$? var:'$var' OPTIND:$OPTIND"