Code cleanups so that libgit.a does not depend on anything in the
builtin/ directory.
* nd/builtin-to-libgit:
fetch-pack: move core code to libgit.a
fetch-pack: remove global (static) configuration variable "args"
send-pack: move core code to libgit.a
Move setup_diff_pager to libgit.a
Move print_commit_list to libgit.a
Move estimate_bisect_steps to libgit.a
Move try_merge_command and checkout_fast_forward to libgit.a