Merge branch 'mm/verify-filename-fix'

"git diff COPYING HEAD:COPYING" gave a nonsense error message that
claimed that the treeish HEAD did not have COPYING in it.

diff --cc builtin/grep.c
Simple merge

diff --cc builtin/rev-parse.c
Simple merge

diff --cc cache.h
Simple merge

diff --cc revision.c
Simple merge

diff --cc setup.c
Simple merge

diff --cc sha1_name.c
Simple merge