Re: [PATCH 1/2 v2] Add strbuf_vaddf(), use it in strbuf_addf(), and add strbuf_initf()

> The most common use of addf() was to init a strbuf and addf() right away.
> Since it is so common, it makes sense to have a function strbuf_initf() to
> wrap both calls into one.
> 
> To do that, we implement a (really minimal) vaddf() lookalike to
> vsprintf().
> 
> At the moment, it only handles %u, %i, %d, %l, %o, %x and %X with size
> indicators '<number>', ' <number>' and '0<number>', as well as %c and %s,
> the latter with size indicators '.*' in addition to the same size
> indicators as for numbers.