Merge remote-tracking branch 'origin/edit' into next

Merge remote-tracking branch 'origin/edit' into next

* origin/edit:
  edit: unlink temporary file when done
  v2writable: replace: kill git processes before reindexing
  edit: drop unwanted headers before noop check
  edit|purge: improve output on rewrites
  edit: new tool to perform edits
  doc: document the --prune option for -index
  admin: expose ->config
  AdminEdit: move editability checks from -purge
  admin: beef up resolve_inboxes to handle purge options
  purge: start moving common options to AdminEdit module
  admin: remove warning arg for unconfigured inboxes
  v2writable: implement ->replace call
  import: switch to "replace_oids" interface for purge
  import: extract_author_info becomes extract_commit_info
  v2writable: consolidate overview and indexing call