bug#10911: 24.0.94; `ido-read-directory-name' should offer known hosts for completion

[Oleksandr Manzyuk]

This is a feature request rather than a bug.  `ido-read-directory-name'
doesn't offer known hosts for completion, unlike `ido-read-file-name'.
Here is what I mean by that.  I'm assuming that `ido-mode' is on.
Please forgive me if I belabor the point.

When I type C-x C-f // and hit TAB, I obtain an *Ido Completions* buffer
containing not only local directory names (bin/, boot/, dev/ etc.), but
also known hosts, which is very convenient in conjunction with TRAMP.  I
can type C-x C-f // g o RET, which expands into /golconda.cs.nuim.ie:,
and if I already have a remote shell running on that host, I can see a
list of files and directories there.  If there is no remote shell yet, I
can simply hit RET, and it will be opened using TRAMP.  Of course, I can
open a dired buffer visiting a remote directory this way, but it should
also be equally convenient to do that with `ido-dired'.  While it is
possible, it is also less convenient: I have to type C-x d //, type the
host name followed by colon *in full and without completion*.

Summarizing, there is a discrepancy in how `ido-read-directory-name' and
`ido-read-file-name' generate completions, and I don't see why this
should be the case.

While I'm happy with C-x C-f for opening dired buffers, also on remote
hosts, having `ido-read-directory-name' complete known hosts would make
this function more useful for other purposes.  For example, I have the
following function:

(defun named-shell (name directory)
  "Open a named shell. NAME is the base name of the shell buffer,
and DIRECTORY is the directory to open the shell in."
  (interactive "MName: \nDDirectory: ")
  (switch-to-buffer (concat "*" name "*"))
  (cd directory)
  (shell (current-buffer)))

I introduced it primarily to be able to quickly open inferior remote
shells.  However, when I'm queried for the directory to open the shell
in, I still have to type in the host name in full.


In GNU Emacs 24.0.94.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.20.1)
 of 2012-02-28 on pandora
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
Configured using:
 `configure '--prefix=/home/manzyuk''

Important settings:
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Major mode: Lisp Interaction

Minor modes in effect:
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o r t SPC e m a c s SPC b u g <return>

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