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, 11 insertions, 10 deletions

diff --git a/test/arg-test.c b/test/arg-test.c
index 736686de..10dc0683 100644
--- a/test/arg-test.c
+++ b/test/arg-test.c
@@ -9,25 +9,26 @@ int main(int argc, char **argv){
     int kw_val=0;
     int fl_val=0;
     int int_val=0;
-    char *pos_arg1=NULL;
-    char *pos_arg2=NULL;
-    char *string_val=NULL;
+    const char *pos_arg1=NULL;
+    const char *pos_arg2=NULL;
+    const char *string_val=NULL;
 
     notmuch_opt_desc_t options[] = {
-	{ NOTMUCH_OPT_KEYWORD, &kw_val, "keyword", 'k',
+	{ .opt_keyword = &kw_val, .name = "keyword", .keywords =
 	  (notmuch_keyword_t []){ { "one", 1 },
 				  { "two", 2 },
 				  { 0, 0 } } },
-	{ NOTMUCH_OPT_KEYWORD_FLAGS, &fl_val, "flag", 'f',
+	{ .opt_flags = &fl_val, .name = "flag", .keywords =
 	  (notmuch_keyword_t []){ { "one",   1 << 0},
 				  { "two",   1 << 1 },
 				  { "three", 1 << 2 },
 				  { 0, 0 } } },
-	{ NOTMUCH_OPT_INT, &int_val, "int", 'i', 0},
-	{ NOTMUCH_OPT_STRING, &string_val, "string", 's', 0},
-	{ NOTMUCH_OPT_POSITION, &pos_arg1, 0,0, 0},
-	{ NOTMUCH_OPT_POSITION, &pos_arg2, 0,0, 0},
-	{ 0, 0, 0, 0, 0 } };
+	{ .opt_int = &int_val, .name = "int" },
+	{ .opt_string = &string_val, .name = "string" },
+	{ .opt_position = &pos_arg1 },
+	{ .opt_position = &pos_arg2 },
+	{ }
+    };
 
     opt_index = parse_arguments(argc, argv, options, 1);