Restructure "reflog expire" to fit the reflogs better with the
recently updated ref API.
Looked reasonable (except that some shortlog entries stood out like
a sore thumb).
* mh/reflog-expire: (24 commits)
refs.c: let fprintf handle the formatting
refs.c: don't expose the internal struct ref_lock in the header file
lock_any_ref_for_update(): inline function
refs.c: remove unlock_ref/close_ref/commit_ref from the refs api
reflog_expire(): new function in the reference API
expire_reflog(): treat the policy callback data as opaque
Move newlog and last_kept_sha1 to "struct expire_reflog_cb"
expire_reflog(): move rewrite to flags argument
expire_reflog(): move verbose to flags argument
expire_reflog(): pass flags through to expire_reflog_ent()
struct expire_reflog_cb: a new callback data type
Rename expire_reflog_cb to expire_reflog_policy_cb
expire_reflog(): move updateref to flags argument
expire_reflog(): move dry_run to flags argument
expire_reflog(): add a "flags" argument
expire_reflog(): extract two policy-related functions
Extract function should_expire_reflog_ent()
expire_reflog(): use a lock_file for rewriting the reflog file
expire_reflog(): return early if the reference has no reflog
expire_reflog(): rename "ref" parameter to "refname"
...