Merge branch 'cc/shared-index-permfix'

The split index code did not honor core.sharedrepository setting
correctly.

* cc/shared-index-permfix:
t1700: make sure split-index respects core.sharedrepository
t1301: move modebits() to test-lib-functions.sh
read-cache: use shared perms when writing shared index

diff --cc read-cache.c
Simple merge