Re: [PATCH 6/6] format-patch: simplify after-subject MIME header handling

> In log_write_email_headers(), we append our MIME headers to the set of
> extra headers by creating a new strbuf, adding the existing headers, and
> then adding our new ones.  We had to do it this way when our output
> buffer might point to the constant opt->extra_headers variable.
>
> But since the previous commit, we always make a local copy of that
> variable. Let's turn that into a strbuf, which lets the MIME code simply
> append to it. That simplifies the function and avoids a pointless extra
> copy of the headers.
>
> Signed-off-by: Jeff King <peff@peff.net>