Jeff King authored Jun 10, 2014 and Junio C Hamano committed Jun 12, 2014

While strbufs are pretty common throughout our code, it is
more flexible for functions to take a pointer/len pair than
a strbuf. It's easy to turn a strbuf into such a pair (by
dereferencing its members), but less easy to go the other
way (you can strbuf_attach, but that has implications about
memory ownership).

This patch teaches commit_tree (and its associated callers
and sub-functions) to take such a pair for the commit
message rather than a strbuf.  This makes passing the buffer
around slightly more verbose, but means we can get rid of
some dangerous strbuf_attach calls in the next patch.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>