chcp: fix inverted logic in argument parsing

Since commit 7aae659 ("chcp: fix segfault"), the logic to
distinguish between the optional device argument and the checkpoint
number list has been inverted.

The code intended to check if the current argument is *not* a valid
checkpoint number (indicating it is a device string).  However, due to
a logic error in that commit, if the argument is not a number (e.g.
"/dev/sda1"), it sets the device to NULL (implying no device argument).
Conversely, if it is a number, it incorrectly consumes it as a device
name.

This causes chcp to fail with "invalid checkpoint number" when a device
is explicitly specified, because the parser fails to advance past the
device string, subsequently attempting to parse the device name as a
checkpoint number in the main loop.

Fix this regression by correcting the if-else branch assignments.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Fixes: 7aae659 ("chcp: fix segfault")

Author: konis

bin/chcp.c

@@ -118,9 +118,9 @@ int main(int argc, char *argv[])
 		modestr = argv[optind++];
 		cno = nilfs_parse_cno(argv[optind], &endptr, CHCP_BASE);
 		if (cno >= NILFS_CNO_MAX || *endptr != '\0')
-			dev = NULL;
-		else
 			dev = argv[optind++];
+		else
+			dev = NULL;
 	}
 
 	if (strcmp(modestr, CHCP_MODE_CP) == 0)