common.c: add more metachars in reject_meta_chars()

Add:

* `#$|`

Ignore:

* `'()~`

Note: `,` does not appear to be a metacharacter, but it (and `%`) are
checked in test/fcopy/cmdline.exp.  I'm not sure if they matter for
fcopy, so they are left as is.

Misc: `$` was suggested by @rusty-snake[1].

This is a follow-up to #7183.

Relates to #3001 #3156 #4614.

[1] https://github.com/netblue30/firejail/pull/7183#issuecomment-4709569497

src/lib/common.c

@@ -484,8 +484,15 @@ void reject_cntrl_chars(const char *fname) {
 	}
 }
 
+// Note: Characters intentionally ignored:
+//
+// * `'`: Used in some dirnames (see #4614).
+// * `()`: Used in some dirnames (see #3001 #3156).
+// * `~`: Might be useful for expansion and seems unlikely to cause problems by
+//        itself.
 #ifndef METACHARS
-#define METACHARS "!\"%&,;<>\\^`{}"
+// All metachars except for ignored chars and chars in other groups.
+#define METACHARS "!\"#$%&',;<>\\^`{|}"
 #endif
 #ifndef GLOBCHARS
 #define GLOBCHARS "*?[]"