Re: [PATCH 0/6] Compute and consume generation numbers

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On 4/3/2018 12:51 PM, Derrick Stolee wrote:
This is the first of several "small" patches that follow the serialized
Git commit graph patch (ds/commit-graph).

As described in Documentation/technical/commit-graph.txt, the generation
number of a commit is one more than the maximum generation number among
its parents (trivially, a commit with no parents has generation number
one).

This series makes the computation of generation numbers part of the
commit-graph write process.

Finally, generation numbers are used to order commits in the priority
queue in paint_down_to_common(). This allows a constant-time check in
queue_has_nonstale() instead of the previous linear-time check.

This does not have a significant performance benefit in repositories
of normal size, but in the Windows repository, some merge-base
calculations improve from 3.1s to 2.9s. A modest speedup, but provides
an actual consumer of generation numbers as a starting point.

A more substantial refactoring of revision.c is required before making
'git log --graph' use generation numbers effectively.

This patch series depends on v7 of ds/commit-graph.

Derrick Stolee (6):
   object.c: parse commit in graph first
   commit: add generation number to struct commmit
   commit-graph: compute generation numbers
   commit: sort by generation number in paint_down_to_common()
   commit.c: use generation number to stop merge-base walks
   commit-graph.txt: update design doc with generation numbers

This patch is also available as a GitHub pull request [1]

[1] https://github.com/derrickstolee/git/pull/5



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