Merge branch 'tr/previous-branch'

Merge branch 'tr/previous-branch'

* tr/previous-branch:
  t1505: remove debugging cruft
  Simplify parsing branch switching events in reflog
  Introduce for_each_recent_reflog_ent().
  interpret_nth_last_branch(): plug small memleak
  Fix reflog parsing for a malformed branch switching entry
  Fix parsing of @{-1}@{1}
  interpret_nth_last_branch(): avoid traversing the reflog twice
  checkout: implement "-" abbreviation, add docs and tests
  sha1_name: support @{-N} syntax in get_sha1()
  sha1_name: tweak @{-N} lookup
  checkout: implement "@{-N}" shortcut name for N-th last branch

Conflicts:
	sha1_name.c