Merge branch 'jl/interrupt-clone-remove-separate-git-dir' into maint

When "git clone --separate-git-dir=$over_there" is interrupted, it failed to remove the real location of the $GIT_DIR it created. This was most visible when interrupting a submodule update. * jl/interrupt-clone-remove-separate-git-dir: clone: support atomic operation with --separate-git-dir