Re: [PATCH 4/5] commit-graph: be extra careful about mixed generations

> From: Derrick Stolee <dstolee@microsoft.com>
>
> When upgrading to a commit-graph with corrected commit dates from
> one without, there are a few things that need to be considered.
>
> When computing generation numbers for the new commit-graph file that
> expects to add the generation_data chunk with corrected commit
> dates, we need to ensure that the 'generation' member of the
> commit_graph_data struct is set to zero for these commits.
>
> Unfortunately, the fallback to use topological level for generation
> number when corrected commit dates are not available are causing us
> harm here: parsing commits notices that read_generation_data is
> false and populates 'generation' with the topological level.
>
> The solution is to iterate through the commits, parse the commits
> to populate initial values, then reset the generation values to
> zero to trigger recalculation. This loop only occurs when the
> existing commit-graph data has no corrected commit dates.
>
> While this improves our situation somewhat, we have not completely
> solved the issue for correctly computing generation numbers for mixes

> layers. That follows in the next change.
>
> Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
> ---
>  commit-graph.c | 32 +++++++++++++++++++++++---------
>  1 file changed, 23 insertions(+), 9 deletions(-)