Remove the mode stuff

It's usefulness is questionable at the moment. Maybe later we will
implement something like this when it's more clear how to use this tool.

lit.c

@@ -667,23 +667,12 @@ void markup_to_program(String_View content, FILE *stream, char *begin, char *end
     }
 }
 
-void program_to_markup(String_View content, FILE *stream, char *begin, char *end, char *comment)
-{
-    (void) content;
-    (void) stream;
-    (void) begin;
-    (void) end;
-    (void) comment;
-    assert(0 && "TODO: program_to_markup not implemented");
-}
-
 int main(int argc, char **argv)
 {
     bool *help = flag_bool("help", false, "Print this help to stdout and exit with 0.");
     char **begin = flag_str("begin", "\\begin{code}", "Line that denotes the beginning of the code block in the markup language.");
     char **end = flag_str("end", "\\end{code}", "Line that denotes the end of the code block in the markup language.");
     char **comment = flag_str("comment", "//", "The inline comment of the programming language.");
-    char **mode = flag_str("mode", "m2p", "Conversion mode. m2p -- markup to program. p2m -- program to markup.");
 
     if (!flag_parse(argc, argv)) {
         usage(stderr);
@@ -724,15 +713,7 @@ int main(int argc, char **argv)
     // TODO: output directly to a file without the need to redirect anything
 
     String_View content = sv_from_parts(mf.content_data, mf.content_size);
-    if (strcmp(*mode, "m2p") == 0) {
-        markup_to_program(content, stdout, *begin, *end, *comment);
-    } else if (strcmp(*mode, "p2m") == 0) {
-        program_to_markup(content, stdout, *begin, *end, *comment);
-    } else {
-        usage(stderr);
-        fprintf(stderr, "ERROR: unknown mode %s\n", *mode);
-        exit(1);
-    }
+    markup_to_program(content, stdout, *begin, *end, *comment);
 
     mf_unmap(&mf);