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

"merge-recursive" was broken in 1.7.7 era and stopped working in an
empty (temporary) working tree, when there are renames involved.
This has been corrected.

* 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