builtin-branch: use strbuf in fill_tracking_info()
builtin-branch: use strbuf in fill_tracking_info()

This is just about using the API, though in case of ~ 10^100 commits,
this would fix the problem of writing to unallocated memory as well. ;-)

Signed-off-by: Miklos Vajna <16f13092e03e3d9e997de904d0f86cc803fb6ef7@frugalware.org>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git