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, 3 insertions, 0 deletions

diff --git a/src/goto-commands.c b/src/goto-commands.c
index 97c58d0..d95886d 100644
--- a/src/goto-commands.c
+++ b/src/goto-commands.c
@@ -218,6 +218,9 @@ teco_state_blockcomment_input(teco_machine_main_t *ctx, gunichar chr, GError **e
 
 TECO_DEFINE_STATE_COMMENT(teco_state_blockcomment);
 
+/*
+ * `!!` line comments are inspired by TECO-64.
+ */
 static teco_state_t *
 teco_state_eolcomment_input(teco_machine_main_t *ctx, gunichar chr, GError **error)
 {