[PATCH v4 0/2] revision.c: implement --reverse=before for walks

v4 aligns the behaviour for --reverse=before and --reverse=after on negative numbers that are less than -1 to treat them the same as -1, which is current behaviour (before this series).

[1/2] revision.c: implement --reverse=before for walks (Mirko Faina) [2/2] revision.c: reduce memory usage on reverse before (Mirko Faina)

 Documentation/rev-list-options.adoc | 16 +++++--
 revision.c                          | 73 +++++++++++++++++++++++++++--
 revision.h                          |  8 +++-
 t/t4202-log.sh                      | 66 ++++++++++++++++++++++++++
 4 files changed, 153 insertions(+), 10 deletions(-)

Range-diff against v3:
1:  4864ac46dd = 1:  4864ac46dd revision.c: implement --reverse=before for walks
2:  00489b0e52 ! 2:  7c0bab5d14 revision.c: reduce memory usage on reverse before
    @@ Commit message
         revision with --reverse=before and --max-count=<k>. We do this through a
         simple queue. With N nodes and K as the --max-count argument, assuming K
         < N, we go from a space complexity of O(N) to O(K). When it comes down
    -    to time complexity, the queue has an ammortized time of O(1) for pops,
    -    so the complexity remains O(N).
    +    to time complexity, the queue has an amortized time of O(1) for pops, so
    +    the complexity remains O(N).
     
         Signed-off-by: Mirko Faina <mroik@delayed.space>
     
    @@ revision.c: struct commit *get_revision(struct rev_info *revs)
      		reversed = NULL;
     -		while ((c = get_revision_internal(revs)))
     -			commit_list_insert(c, &reversed);
    -+		if (revs->reverse == REVERSE_BEFORE && max_count != -1) {
    ++		if (revs->reverse == REVERSE_BEFORE && max_count >= 0) {
     +			retrieve_with_window(revs, max_count, &reversed);
     +		} else {
     +			while ((c = get_revision_internal(revs)))

base-commit: e8955061076952cc5eab0300424fc48b601fe12d