fixed serious bug with certain alternative string termination chars in commands with multiple string arguments

* When `@`-modifying a command with several string arguments and choosing `{` as the alternative
  string termination character, the parser would get totally confused.
  Any sequence of `{` would be ignored and only the first non-`{` would become the termination character.
  Consequently you also couldn't choose a new terminator after the closing `}`.
  So even a documented code example from sciteco(7) wouldn't work.
  The same was true when using $ (escape) or ^A as the alternative termination character.
* We can now correctly parse e.g. `@FR{foo}{bar}` or `@FR$foo$bar$` (even though the
  latter one is quite pointless).
* has probably been broken forever (has been broken even before v2.0).
* Whitespace is now ignored in front of alternative termination characters as in TECO-64, so
  we can also write `@S /foo/` or even
  ```
  @^Um
  {
    !* blabla *!
  }
  ```
  I wanted to disallow whitespace termination characters, so the alternative would have been
  to throw an error.
  The new implementation at least adds some functionality.
  * Avoid redundancies when parsing no-op characters via teco_is_noop().
    I assume that this is inlined and drawn into any jump-table what would be
    generated for the switch-statement in teco_state_start_input().
 * Alternative termination characters are still case-folded, even if they are Unicode glyphs,
   so `@IЖfooж` would work and insert `foo`.
   This should perhaps be restricted to ANSI characters?

1 files changed, 4 insertions, 7 deletions

diff --git a/src/core-commands.c b/src/core-commands.c
index c71ee95..f384272 100644
--- a/src/core-commands.c
+++ b/src/core-commands.c
@@ -722,24 +722,21 @@ teco_state_start_input(teco_machine_main_t *ctx, gunichar chr, GError **error)
 		['T']  = {&teco_state_start, teco_state_start_typeout}
 	};
 
-	switch (chr) {
 	/*
-	 * No-ops (same as TECO_NOOPS):
+	 * Non-operational commands.
 	 * These are explicitly not handled in teco_state_control,
 	 * so that we can potentially reuse the upcaret notations like ^J.
 	 */
-	case ' ':
-	case '\f':
-	case '\r':
-	case '\n':
-	case '\v':
+	if (teco_is_noop(chr)) {
 		if (ctx->flags.modifier_at ||
 		    (ctx->flags.mode == TECO_MODE_NORMAL && ctx->flags.modifier_colon)) {
 			teco_error_modifier_set(error, chr);
 			return NULL;
 		}
 		return &teco_state_start;
+	}
 
+	switch (chr) {
 	/*$ 0 1 2 3 4 5 6 7 8 9 digit number
 	 * [n]0|1|2|3|4|5|6|7|8|9 -> n*Radix+X -- Append digit
 	 *