Merge branch 'js/mingw-loosen-overstrict-tree-entry-checks'

An earlier update to Git for Windows declared that a tree object is invalid if it has a path component with backslash in it, which was overly strict, which has been corrected. The only protection the Windows users need is to prevent such path (or any path that their filesystem cannot check out) from entering the index. * js/mingw-loosen-overstrict-tree-entry-checks: mingw: only test index entries for backslashes, not tree entries