Re: [PATCH v1 10/19] read-cache: regenerate shared index if necessary

> When writing a new split-index and there is a big number of cache
> entries in the split-index compared to the shared index, it is a
> good idea to regenerate the shared index.
> 
> By default when the ratio reaches 20%, we will push back all
> the entries from the split-index into a new shared index file
> instead of just creating a new split-index file.
> 
> The threshold can be configured using the
> "splitIndex.maxPercentChange" config variable.
> 
> We need to adjust the existing tests in t1700 by setting
> "splitIndex.maxPercentChange" to 100 at the beginning of t1700,
> as the existing tests are assuming that the shared index is
> regenerated only when `git update-index --split-index` is used.
> 
> Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
> ---
>  read-cache.c           | 33 ++++++++++++++++++++++++++++++++-
>  t/t1700-split-index.sh |  1 +
>  2 files changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/read-cache.c b/read-cache.c
> index bb53823..a91fabe 100644
> --- a/read-cache.c
> +++ b/read-cache.c
> @@ -2216,6 +2216,36 @@ static int write_shared_index(struct index_state *istate,
>  	return ret;
>  }
>  
> +static const int default_max_percent_split_change = 20;
> +
> +int too_many_not_shared_entries(struct index_state *istate)