Merge branch 'bk/refresh-missing-ok-in-merge-recursive'

Allow "merge-recursive" to work in an empty (temporary) working
tree again when there are renames involved, correcting an old
regression in 1.7.7 era.

* bk/refresh-missing-ok-in-merge-recursive:
merge-recursive.c: tolerate missing files while refreshing index
read-cache.c: extend make_cache_entry refresh flag with options
read-cache.c: refactor --ignore-missing implementation
t3030-merge-recursive: test known breakage with empty work tree

diff --cc cache.h
Simple merge

diff --cc merge-recursive.c
Simple merge

diff --cc read-cache.c
Simple merge