Merge branch 'rs/fsck-duplicate-names-in-trees'

The check in "git fsck" to ensure that the tree objects are sorted still had corner cases it missed unsorted entries. * rs/fsck-duplicate-names-in-trees: fsck: detect more in-tree d/f conflicts t1450: demonstrate undetected in-tree d/f conflict t1450: increase test coverage of in-tree d/f detection fsck: fix a typo in a comment