`mke2fs` has a `-d` option that allows to populate the newly created filesystem without needing to temporarily mount it. That allows to use `parted` and `mkfs.ext3` on regular files without needing root access.
There is nothing temporary about our "tmpdir" - its sole purpose is to
contain the final product of the bootstrap process. Thus, removing it
at the end of bootstrap amounts to doing the entire process for nothing.
To remedy this, --tmpdir is renamed --target, keeping the -t short form,
and defaulting to "target" instead of "tmp" to make its purpose clearer.
The --preserve option is removed, as the target is now always preserved.
Eduardo Sánchez Muñoz
Gábor Stefanik