`--add-file` adds only the `--prefix` joined with the basename of the added file, so, adding a folder like `vendor` would break havoc.
this basically writes our own source archives (which are more compressed) and allows to add an entire folder easily, as well as other mappings as `archives` already supports.
refs #3102#2911
Signed-off-by: Carlos A Becker <caarlos0@users.noreply.github.com>