[O] copying files in the links while exporting to html

[zhenjiang zech xu]

Hi orgmoders,

Is there any existing function to copy files in the external links to a specified location when exporting .org file to html? I know org-publish has functionality to copy files with certain suffices on defined project, but my need is to export single file or single subtree in the buffer.

For example, when I export the following subtree, it would be lovely to copy the spam.png to the path I set up.

* foo
  [[file:spam.png]]

If there is no function ready to do that, what is the easiest easy to implement it? any point to the right direction is appreciated.

Thanks,

Zhenjiang