* src/regex-emacs.c (analyze_first): Fix incorrect optimization

The optimization was incorrect in a particular corner case.
In this fix I just disable it conservatively for more cases because
it's not obvious how to fix it while preserving the "good" cases.

We may find a better fix by using an approach like the one
in `mutually_exhaustive_aux`, but for now this is good enough,
especially since \{..\} repetitions are not used very frequently.

* test/src/regex-resources/PTESTS: New test.

src/regex-emacs.c

@@ -3086,8 +3086,10 @@ analyze_first (re_char *p, re_char *pend, char *fastmap, bool multibyte)
 	  /* We only care about one iteration of the loop, so we don't
 	     need to consider the case where this behaves like an
 	     on_failure_jump.  */
-	  continue;
-
+	  /* FIXME: Sadly, the above is not true when the loop's body
+	     can match the empty string :-(  */
+	  /* continue; */
+	  return -1;
 
 	case set_number_at:
 	  p += 4;

test/src/regex-resources/PTESTS

@@ -269,6 +269,7 @@
 #W the expected result for \([a-c]*\)\{2,\} is failure which isn't correct
 1¦3¦\([a-c]*\)\{2,\}¦abcdefg¦
 1¦3¦\([a-c]*\)\{1,\}¦abcdefg¦
+0¦0¦\([a-c]*\)\{2,\}¦gabcdefg¦
 -1¦-1¦a\{64,\}¦aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa¦
 # GA142
 1¦3¦a\{2,3\}¦aaaa¦