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 <redacted>
---
 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)