Merge branch 'jk/fast-import-cleanup'

Code clean-up.

* jk/fast-import-cleanup:
pack.h: define largest possible encoded object size
encode_in_pack_object_header: respect output buffer length
fast-import: use xsnprintf for formatting headers
fast-import: use xsnprintf for writing sha1s

diff --cc builtin/pack-objects.c
Simple merge

diff --cc fast-import.c
Simple merge