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