[PATCH v2 0/9] misc commit-graph and oid-array cleanups

Here's a re-roll of my series to clean up commit-graph and oid-array. The changes are all cosmetic: comments and commit messages (and most of those just in the for-loop patch). I recommend just reading the range-diff below, if you reviewed v1.

  [1/9]: oid-array.h: drop sha1 mention from header guard
  [2/9]: t0064: drop sha1 mention from filename
  [3/9]: t0064: make duplicate tests more robust
  [4/9]: cache.h: move hash/oid functions to hash.h
  [5/9]: oid-array: make sort function public
  [6/9]: oid-array: provide a for-loop iterator
  [7/9]: commit-graph: drop count_distinct_commits() function
  [8/9]: commit-graph: replace packed_oid_list with oid_array
  [9/9]: commit-graph: use size_t for array allocation and indexing

 cache.h                                       |  94 ---------------
 commit-graph.c                                | 107 +++---------------
 hash.h                                        |  95 ++++++++++++++++
 oid-array.c                                   |  17 ++-
 oid-array.h                                   |  34 +++++-
 t/{t0064-sha1-array.sh => t0064-oid-array.sh} |   9 +-
 6 files changed, 157 insertions(+), 199 deletions(-)
 rename t/{t0064-sha1-array.sh => t0064-oid-array.sh} (90%)

Range-diff from v1:

 1:  7cfd2f9a29 =  1:  1b52a4ea67 oid-array.h: drop sha1 mention from header guard
 2:  82b8902560 =  2:  96ef8b8bb8 t0064: drop sha1 mention from filename
 3:  b69af2f0d5 =  3:  7382ad6d52 t0064: make duplicate tests more robust
 4:  0e258a486a =  4:  a0b8b9aabf cache.h: move hash/oid functions to hash.h
 5:  1ed342fe20 =  5:  336650a307 oid-array: make sort function public
 6:  28893c76f8 !  6:  cc1c2a16da oid-array: provide a for-loop iterator
    @@ oid-array.h: void oid_array_filter(struct oid_array *array,
      void oid_array_sort(struct oid_array *array);
      
     +/**
    -+ * Find the next unique oid in the array after position "cur". You
    -+ * can use this to iterate over unique elements, like:
    ++ * Find the next unique oid in the array after position "cur".
    ++ * The array must be sorted for this to work. You can iterate
    ++ * over unique elements like this:
     + *
     + *   size_t i;
     + *   oid_array_sort(array);
 7:  d025d6215c !  7:  16fd32e41c commit-graph: drop count_distinct_commits() function
    @@ Commit message
         the count are:
     
           - check if our count will overflow our data structures. But the limit
    -        there is 2^31 commits, so it's not likely to happen in practice.
    +        there is 2^31 commits, so while this is a useful check, the
    +        off-by-one is not likely to matter.
     
           - pre-allocate the array of commit pointers. But over-allocating by
    -        one isn't a problem.
    +        one isn't a problem; we'll just waste a few extra bytes.
     
         The bug would be easy enough to fix, but we can observe that neither of
    -    those steps is necessary. We'll check the count of the commit array
    -    after we build it anyway, so checking at this point is redundant. And we
    -    use ALLOC_GROW() when building the commit array, so there's no need to
    -    preallocate it (it's possible that doing so is slightly more efficient,
    -    but if we care we can just optimistically allocate one slot for each
    -    oid; I didn't bother here).
    +    those steps is necessary.
    +
    +    After building the actual commit array, we'll likewise check its count
    +    for overflow. So the extra check of the distinct commit count here is
    +    redundant.
    +
    +    And likewise we use ALLOC_GROW() when building the commit array, so
    +    there's no need to preallocate it (it's possible that doing so is
    +    slightly more efficient, but if we care we can just optimistically
    +    allocate one slot for each oid; I didn't bother here).
     
         So count_distinct_commits() isn't doing anything useful. Let's just get
         rid of that step.
     
         Note that a side effect of the function was that we sorted the list of
         oids, which we do rely on in copy_oids_to_commits(), since it must also
    -    skip the duplicates. So we'll move the qsort there.
    +    skip the duplicates. So we'll move the qsort there. I didn't copy the
    +    "TODO" about adding more progress meters. It's actually quite hard to
    +    make a repository large enough for this qsort would take an appreciable
    +    amount of time, so this doesn't seem like a useful note.
     
         Signed-off-by: Jeff King <peff@peff.net>
     
 8:  55d6052e0d =  8:  b0f6326fbe commit-graph: replace packed_oid_list with oid_array
 9:  c9c6e2de47 =  9:  89848e2214 commit-graph: use size_t for array allocation and indexing