cli: use designated initializers for opt desc

Several changes at once, just to not have to change the same lines
several times over:

- Use designated initializers to initialize opt desc arrays.

- Only initialize the needed fields.

- Remove arg_id (short options) as unused.

- Replace opt_type and output_var with several type safe output
  variables, where the output variable being non-NULL determines the
  type. Introduce checks to ensure only one is set. The downside is
  some waste of const space per argument; this could be saved by
  retaining opt_type and using a union, but that's still pretty
  verbose.

- Fix some variables due to the type safety. Mostly a good thing, but
  leads to some enums being changed to ints. This is pedantically
  correct, but somewhat annoying. We could also cast, but that defeats
  the purpose a bit.

- Terminate the opt desc arrays using {}.

The output variable type safety and the ability to add new fields for
just some output types or arguments are the big wins. For example, if
we wanted to add a variable to set when the argument is present, we
could do so for just the arguments that need it.

Beauty is in the eye of the beholder, but I think this looks nice when
defining the arguments, and reduces some of the verbosity we have
there.

1 files changed, 4 insertions, 4 deletions

diff --git a/notmuch-compact.c b/notmuch-compact.c
index 855545d7..ae464e48 100644
--- a/notmuch-compact.c
+++ b/notmuch-compact.c
@@ -36,10 +36,10 @@ notmuch_compact_command (notmuch_config_t *config, int argc, char *argv[])
     int opt_index;
 
     notmuch_opt_desc_t options[] = {
-	{ NOTMUCH_OPT_STRING, &backup_path, "backup", 0, 0 },
-	{ NOTMUCH_OPT_BOOLEAN,  &quiet, "quiet", 'q', 0 },
-	{ NOTMUCH_OPT_INHERIT, (void *) &notmuch_shared_options, NULL, 0, 0 },
-	{ 0, 0, 0, 0, 0}
+	{ .opt_string = &backup_path, .name = "backup" },
+	{ .opt_bool =  &quiet, .name = "quiet" },
+	{ .opt_inherit = notmuch_shared_options },
+	{ }
     };
 
     opt_index = parse_arguments (argc, argv, options, 1);