Merge branch 'sp/pack'

Merge branch 'sp/pack'

* sp/pack:
  Style nit - don't put space after function names
  Ensure the pack index is opened before access
  Simplify index access condition in count-objects, pack-redundant
  Test for recent rev-parse $abbrev_sha1 regression
  rev-parse: Identify short sha1 sums correctly.
  Attempt to delay prepare_alt_odb during get_sha1
  Micro-optimize prepare_alt_odb
  Lazily open pack index files on demand