sftp versus application-specific (or restricted) shell

["Cathey, Jim" <jcathey@xxxxxxxxx>]

We have an application-specific 'shell' that is completely unrelated to
Bourne/C-shell world, yet we would like sftp to work.  What we've found
is
that sshd (in session.c) EXPECTS that ANY shell be able to execute
"anyshell
-c /path/to/sftp" and have it end up execing sftp.  Ours won't, nor for
that
matter, does rbash, since sftp has slashes in the path.

This seems like a coding error to me, why should session.c not do the
old-school canonical Unix-ey thing of trying to exec(command) first,
before
going on to try exec(shell, "-c", command), if its ultimate purpose was
to
execute command?  Is there a reason, or is this just a long-standing
'bug'? 
What purpose does first trotting through a user's Bourne-y shell serve?

-- Jim