Merge branch 'jk/oid-array-cleanup'

Code clean-up. * jk/oid-array-cleanup: commit-graph: use size_t for array allocation and indexing commit-graph: replace packed_oid_list with oid_array commit-graph: drop count_distinct_commits() function oid-array: provide a for-loop iterator oid-array: make sort function public cache.h: move hash/oid functions to hash.h t0064: make duplicate tests more robust t0064: drop sha1 mention from filename oid-array.h: drop sha1 mention from header guard