As a personal project, i'm interested in adding a "-via
[user@]hostname" option to sftp; i.e. an option that will tunnel the
sftp connection through a server before the final destination. The
obvious use for this is for connecting to computers that are behind a
network from outside of the network. I'm aware that this can already
be done using a separate ssh command, or by transferring a given file
to the gateway first before the final destination, but being lazy
users we like simpler and more elegant commands. TightVNC added a
similar "-via" parameter to vncviewer.

I have not worked with the OpenSSH codebase before; does anyone have
any suggestions and/or warnings for where I may trip up? Ideally my
changes would be integrated back into OpenSSH, but if there's a moral
opposition to including this option in sftp, i'm content with this
remaining a personal project.

Thanks for any help,
Miles