session.tes: store the current tab style (width and hard-tabs); fixed for filenames containing ASCII 27

* You can now set a per-file tab style, that differs from the defaults established
  in the ED hook.
  This is important especially since we do not yet support per-project .teco_ini
  scripts where you could establish differing policies depending on the VCS repository.
  (The latter would be easy to implement, but we cannot currently easily extend the
  existing ED hooks.)
* It's unlikely that files contain an ASCII 27, but not impossible.
  Therefore we now use ASCII 0 (^@) as a terminator.
  This indeed be safe under UNIX.
  Even better would be a string building construct for escaping ASCII 27 ($), though,
  as that would work with arbitrary bytes.

2 files changed, 5 insertions, 0 deletions

diff --git a/TODO b/TODO
index c0ff79a..2e3e8a8 100644
--- a/TODO
+++ b/TODO
@@ -566,8 +566,13 @@ Features:
    with --valgrind during CI (Ubuntu).
    This did not work out of the box.
  * session.tes: Perhaps persist the search-replace registers "-" and "_".
+   Unfortunately, there is currently no way to reliably escape their
+   contents in the generated .teco_session.
    Ideally we would also persist any manually configured lexer,
    but we cannot easily store the current buffer's lexer.
+ * session.tes: Could mung a .teco_ini in the VCS directory as well.
+   This is only really useful once we can elegantly append to various
+   ED hooks.
  * grosciteco: Does not currently support diacritics.
    This is because Groff decomposes characters in intermediate output.
    Either we have to consult devutf8/R or use wrap g_unichar_compose().
diff --git a/lib/session.tes b/lib/session.tes
index 598dbca..56634a5 100644
--- a/lib/session.tes
+++ b/lib/session.tes