Merge patch series "regex patches"

Rasmus Villemoes <ravi@prevas.dk> says:

This started as a rather simple patch, 1/12, adding the ability to
more conveniently do regex matching in shell.

But with that, it became very easy to see what the slre library can
and especially what it cannot do, and that way I found both outright
bugs and a "wow, doesn't it support that syntax" gotcha. I couldn't
find any tests ('git grep slre -- test/' was empty), so I added a
small test suite and tweaked slre.c.

Link: https://lore.kernel.org/r/20250513084034.654865-1-ravi@prevas.dk

include/slre.h

@@ -63,7 +63,6 @@ struct slre {
 	int		code_size;
 	int		data_size;
 	int		num_caps;	/* Number of bracket pairs	*/
-	int		anchored;	/* Must match from string start	*/
 	const char	*err_str;	/* Error string			*/
 };