dired-dwim-target (was: FFAP)

[Juri Linkov]

The first thing I have to do when using Dired in pristine Emacs without
.emacs is to type `M-x set-variable RET dired-dwim-target RET t RET'
because without dired-dwim-target = t Dired is helpless to me.

By default Dired operations provide the following minibuffer
default values (0. means initial input, and 1. - minibuffer's
contents after one M-n):

0. current directory name
1. file name from the current Dired line

However, when there is another Dired window on the same frame, there is
no easy way to copy/rename a file to it.  When `dired-dwim-target' is t,
then the default values are:

0. other directory name
1. file name from the other directory

This is better for copying/renaming to another directory, but still
inconvenient for copying/renaming in the current directory.  This
requires deleting all other Dired windows to force it showing the
default with the current directory name.

The solution is simple: provide both the current and other
directory names as default values.  The following patch keeps
the old behavior when there is one Dired window:

0. current directory name
1. file name from the current Dired line

but with more Dired windows it provides more default values:

0. current directory name
1. other directory name
2. file name from the other directory
3. file name from the current Dired line

When there are more than one marked file:

0. current directory name
1. other directory name

When `dired-dwim-target' is t (whose only purpose now will be
to show the other directory name as initial input, but with
`dired-dwim-target' = nil the same will be easily achievable via M-n):

0. other directory name
1. current directory name
2. file name from the current Dired line
3. file name from the other directory

When there are more than one marked file:

0. other directory name
1. current directory name

Actually in the following patch after reaching the end of the
aforementioned lists prepared in `dired-do-create-files-defaults',
the function `read-file-name-defaults' starts adding more items
guessed from the content of the Dired buffer.  But perhaps this
is not too useful.  If so, this can be easily disabled by
setting `minibuffer-default-add-function' to nil in
`dired-do-create-files' (currently commented out).

Index: lisp/dired-aux.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/dired-aux.el,v
retrieving revision 1.197
diff -c -r1.197 dired-aux.el
*** lisp/dired-aux.el   13 Nov 2009 22:19:50 -0000      1.197
--- lisp/dired-aux.el   15 Nov 2009 15:12:05 -0000
***************
*** 1463,1471 ****
                       (expand-file-name (file-name-nondirectory (car fn-list))
                                         target-dir)))
         (target (expand-file-name ; fluid variable inside dired-create-files
!                  (dired-mark-read-file-name
!                   (concat (if dired-one-file op1 operation) " %s to: ")
!                   target-dir op-symbol arg rfn-list default)))
         (into-dir (cond ((null how-to)
                          ;; Allow DOS/Windows users to change the letter
                          ;; case of a directory.  If we don't test these
--- 1463,1477 ----
                       (expand-file-name (file-name-nondirectory (car fn-list))
                                         target-dir)))
         (target (expand-file-name ; fluid variable inside dired-create-files
!                 (minibuffer-with-setup-hook
!                     (lambda ()
!                       ;; (set (make-local-variable 
'minibuffer-default-add-function) nil)
!                       (setq minibuffer-default
!                             (dired-do-create-files-defaults
!                              fn-list target-dir)))
!                   (dired-mark-read-file-name
!                    (concat (if dired-one-file op1 operation) " %s to: ")
!                    target-dir op-symbol arg rfn-list default))))
         (into-dir (cond ((null how-to)
                          ;; Allow DOS/Windows users to change the letter
                          ;; case of a directory.  If we don't test these
***************
*** 1520,1525 ****
--- 1526,1568 ----
     (function read-file-name)
     (format prompt (dired-mark-prompt arg files)) dir default))
  
+ (defun dired-do-create-files-defaults (fn-list target-dir)
+   ;; Return a list of default values for `dired-do-create-files-defaults'.
+   (let (target-dirs)
+     ;; Get a list of directories of visible buffers in dired-mode.
+     (walk-windows (lambda (w)
+                   (with-current-buffer (window-buffer w)
+                     (when (eq major-mode 'dired-mode)
+                       (push default-directory target-dirs)))))
+     ;; Return default values.
+     (cond
+      (dired-dwim-target
+       (setq target-dirs (delete target-dir target-dirs))
+       (if dired-one-file
+         (append target-dirs
+                 (mapcar (lambda (dir)
+                           (expand-file-name
+                            (file-name-nondirectory (car fn-list))
+                            dir))
+                         (reverse target-dirs))
+                 (list (expand-file-name
+                        (file-name-nondirectory (car fn-list))
+                        dir)))
+       target-dirs))
+      (t
+       (setq target-dirs (delete default-directory target-dirs))
+       (if dired-one-file
+         (append target-dirs
+                 (mapcar (lambda (dir)
+                           (expand-file-name
+                            (file-name-nondirectory (car fn-list))
+                            dir))
+                         (reverse target-dirs))
+                 (list (expand-file-name
+                        (file-name-nondirectory (car fn-list))
+                        target-dir)))
+       target-dirs)))))
+ 
  (defun dired-dwim-target-directory ()
    ;; Try to guess which target directory the user may want.
    ;; If there is a dired buffer displayed in the next window, use

Index: lisp/minibuffer.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/minibuffer.el,v
retrieving revision 1.96
diff -c -r1.96 minibuffer.el
*** lisp/minibuffer.el  12 Nov 2009 23:10:06 -0000      1.96
--- lisp/minibuffer.el  15 Nov 2009 15:11:14 -0000
***************
*** 1253,1258 ****
--- 1253,1310 ----
  ;; Not always defined, but only called if next-read-file-uses-dialog-p says 
so.
  (declare-function x-file-dialog "xfns.c"
                    (prompt dir &optional default-filename mustmatch 
only-dir-p))
+ (declare-function dired-get-filename "dired" (&optional localp 
no-error-if-not-filep))
+ 
+ (defun read-file-name-defaults (&optional dir initial)
+   (let ((default
+         (cond
+          ;; With non-nil `initial', use `dir' as the first default.
+          ;; Essentially, this mean reversing the normal order of the
+          ;; current directory name and the current file name, i.e.
+          ;; 1. with normal file reading:
+          ;; 1.1. initial input is the current directory
+          ;; 1.2. the first default is the current file name
+          ;; 2. with non-nil `initial' (for `find-alternate-file'):
+          ;; 2.2. initial input is the current file name
+          ;; 2.1. the first default is the current directory
+          (initial (abbreviate-file-name dir))
+          ;; In file buffers, try to get the current file name
+          (buffer-file-name
+           (abbreviate-file-name buffer-file-name))
+          ;; In Dired, get file name from the current line.
+          ((eq major-mode 'dired-mode)
+           (let ((filename (dired-get-filename nil t)))
+             (when filename
+               (if (file-directory-p filename)
+                   (file-name-as-directory (abbreviate-file-name filename))
+                 (abbreviate-file-name filename)))))))
+       (filename-at-point
+        (cond
+         ((fboundp 'ffap-guesser)
+          ;; Logic from `ffap-read-file-or-url' and `dired-at-point-prompter'
+          (let ((guess (ffap-guesser)))
+            (setq guess
+                  (if (or (not guess)
+                          (and (fboundp 'ffap-url-p)
+                               (ffap-url-p guess))
+                          (and (fboundp 'ffap-file-remote-p)
+                               (ffap-file-remote-p guess)))
+                      guess
+                    (abbreviate-file-name (expand-file-name guess))))
+            (when guess
+              (if (file-directory-p guess)
+                  (file-name-as-directory guess)
+                guess))))
+         ;; ((fboundp 'thing-at-point)
+         ;;  (thing-at-point 'filename))
+         )))
+     (when filename-at-point
+       (setq default (delete-dups
+                    (delete "" (delq nil (list filename-at-point default))))))
+     ;; Append new default values to the end of existing `minibuffer-default'
+     (append
+      (if (listp minibuffer-default) minibuffer-default (list 
minibuffer-default))
+      (if (listp default) default (list default)))))
  
  (defun read-file-name (prompt &optional dir default-filename mustmatch 
initial predicate)
    "Read file name, prompting with PROMPT and completing in directory DIR.
***************
*** 1337,1343 ****
                      (lexical-let ((dir (file-name-as-directory
                                          (expand-file-name dir))))
                        (minibuffer-with-setup-hook
!                           (lambda () (setq default-directory dir))
                          (completing-read prompt 'read-file-name-internal
                                           pred mustmatch insdef
                                           'file-name-history 
default-filename)))
--- 1389,1409 ----
                      (lexical-let ((dir (file-name-as-directory
                                          (expand-file-name dir))))
                        (minibuffer-with-setup-hook
!                           (lambda ()
!                           (setq default-directory dir)
!                           ;; Unless a list of default values is provided,
!                           ;; reset `minibuffer-default' to nil and on the
!                           ;; first request on `M-n' fill it with a list of
!                           ;; default values relevant for file-name reading.
!                           (unless (consp default-filename)
!                             (setq minibuffer-default nil)
!                             (set (make-local-variable 
'minibuffer-default-add-function)
!                                  (lambda ()
!                                    (message "Original buffer: %S"
!                                             (window-buffer 
(minibuffer-selected-window)))
!                                    (with-current-buffer
!                                        (window-buffer 
(minibuffer-selected-window))
!                                      (read-file-name-defaults dir 
initial))))))
                          (completing-read prompt 'read-file-name-internal
                                           pred mustmatch insdef
                                           'file-name-history 
default-filename)))

-- 
Juri Linkov
http://www.jurta.org/emacs/