Merge branch 'dt/merge-recursive-case-insensitive' into maint

On a case insensitive filesystem, merge-recursive incorrectly
deleted the file that is to be renamed to a name that is the same
except for case differences.

* dt/merge-recursive-case-insensitive:
mv: allow renaming to fix case on case insensitive filesystems
merge-recursive.c: fix case-changing merge bug

diff --cc builtin/mv.c
Simple merge