Merge branch 'rs/cat-file-default-format-optim'

The default format path of git cat-file --batch has been optimized
to use strbuf_add_oid_hex() and strbuf_add_uint() instead of
strbuf_addf(), yielding a noticeable speedup.

* rs/cat-file-default-format-optim:
  cat-file: speed up default format

diff --cc builtin/cat-file.c
Simple merge