PATCH: Support file url in _urls

[Oliver Kiddle <opk@xxxxxxxxxxxxx>]

Following is a patch to _urls to allow it to support the file url:
file://<tab>  will complete from .zsh/urls as for http/ftp
file:/<tab>   will complete files from root
file:<tab>    inserts the current directory. I find this behaviour
(which is done in the compctl example) extremely useful.

There is one slight problem: if the current directory is root then the
compadd -S '/' ~+ line will add two slashes - one for the current
directory '/' and one for the suffix. I can't think of a simple way off
the top of my head to chop any trailing slash off the end of ~+.

What is the bookmark url scheme? Is it something specific to Netscape or
Lynx because if so, handling of it should move to _lynx/_netscape. Or,
maybe we need to provide a way of specifying which url schemes are supported.
Lynx supports a finger url for example. 

I'm not entirely convinced by the system of taking urls from a directory
structure. At the least I think there should be an alternative. For
example, if $compconfig[urls_path] doesn't exist, the basic host names
should complete after (http|file|ftp)://. I would also like a compconfig
option which says that the local host is a web server, named X, doc root
in Y and users own web pages in directory Z within their home so files on
a local web server are completed.

One thing which I would like to implement is to restrict file types used
with urls. This would probably depend upon the browser (Netscape handles
graphics, Lynx doesn't etc) but the parameters to _url are passed to
both _files and compadd so I'm restricted in what I can do here.

Shouldn't _webbrowser be ditched and the first line of _urls be changed
to the #compdef - it would be cleaner in my opinion. The only problem is
that the -f option would be lost for those commands. We could always
negate its meaning though.

Any comments?

Oliver Kiddle
*** Completion/User/_urls.bak	Thu Oct  7 12:03:33 1999
--- Completion/User/_urls	Thu Oct  7 12:33:20 1999
***************
*** 46,58 ****
    scheme="${PREFIX%%:*}"
    compset -P "[-+.a-z0-9]#:"
  else
!   compadd "$@" -S '' http:// ftp:// bookmark:
    return
  fi
  
  case "$scheme" in
!   http) compset -P // || { compadd "$@" -S '' //; return };;
!   ftp) compset -P // || { compadd "$@" -S '' //; return };;
  esac
  
  if [[ "$scheme" = bookmark &&
--- 46,68 ----
    scheme="${PREFIX%%:*}"
    compset -P "[-+.a-z0-9]#:"
  else
!   compadd "$@" -S '' http:// ftp:// bookmark: file:
    return
  fi
  
  case "$scheme" in
!   http|ftp) compset -P // || { compadd "$@" -S '' //; return };;
!   file)
!     if [[ -prefix // ]]; then
!       compset -P //
!     elif [ -prefix / ]; then
!       _files "$@"
!       return
!     elif [ ! "$PREFIX" ]; then
!       compadd -S '/' ~+
!       return
!     fi
!   ;;
  esac
  
  if [[ "$scheme" = bookmark &&