I've never accidentally packaged the whole root directory and tried deploying it
but I have confirmed that with an empty sub-directory it comes back quickly.
So I'm not sure what is the root issue here.
The man pages say the operand is a file, not a directory, so if the man pages
are correct it could just check whether a file or directory was specified and
return an error immediately.
If the man pages are wrong, and it is supposed to traverse all subdirectories
searching for applications, then that's an issue by itself. Most Unix but also
Windows commands don't recursively go into each subdirectory unless some
recursive option has been explicitly specified. GF should operate the same.
In my case I tried to specify an application by using tab completion (and who
doesn't) and it picked a directory instead (note that on Windows it picks the
first match and you can cycle through the candidates by pressing tab again).
When this happened to me I didn't actually deploy '\' but still the
sub-directory that was picked had enough files for asadmin to become unresponsive.