Fills the user template with varargs key-value pairs. First argument is the number of pairs. Call e.g. fill(6, "key1", value1, "key2", value2, …). Vala appends null after the last argument; we critical if we get null too early or extra args.
For each key/value pair: if template has {key}, replace with value; or handle DEFAULT / {key/start}..{key/end}.
| n_pairs |
number of key-value pairs |
|
the filled template string |