master 74f15ad72d9 1/2: New variable shell-command-guess-dired-optional (bug#18132)

[Juri Linkov]

branch: master
commit 74f15ad72d937b309dafecba872bccd1a880181e
Author: Juri Linkov <juri@linkov.net>
Commit: Juri Linkov <juri@linkov.net>

    New variable shell-command-guess-dired-optional (bug#18132)
    
    * doc/emacs/dired.texi (Shell Command Guessing):
    Add dired-guess-shell-alist-optional.
    
    * lisp/dired.el (dired-guess-shell-alist-user):
    * lisp/dired-aux.el (dired-do-shell-command):
    Add dired-guess-shell-alist-optional to docstring.
    (dired-guess-shell-alist-default): Move media commands to
    'dired-guess-shell-alist-optional'.
    (dired-guess-shell-alist-optional): New variable.
    (dired-guess-default): Add 'dired-guess-shell-alist-optional'
    to the end after 'dired-guess-shell-alist-user'
    and 'dired-guess-shell-alist-default'.
    (shell-command-guess-functions): Add more options.
    (shell-command-guess-dired): Remove function.
    (shell-command-guess-dired-user)
    (shell-command-guess-dired-default)
    (shell-command-guess-dired-optional): New functions.
---
 doc/emacs/dired.texi |  13 ++++++-
 etc/NEWS             |   4 ++
 lisp/dired-aux.el    | 101 ++++++++++++++++++++++++++++++++++++---------------
 lisp/dired.el        |   5 ++-
 4 files changed, 89 insertions(+), 34 deletions(-)

diff --git a/doc/emacs/dired.texi b/doc/emacs/dired.texi
index a3a740f9727..898c0bfaade 100644
--- a/doc/emacs/dired.texi
+++ b/doc/emacs/dired.texi
@@ -1167,11 +1167,20 @@ guessing off.  The elements of 
@code{dired-guess-shell-alist-user}
 (defined by the user) will override these rules.
 @end defvar
 
+@defvar dired-guess-shell-alist-optional
+This variable is like @code{dired-guess-shell-alist-default} but
+contains external viewers and players for various media formats.
+Setting this to @code{nil} turns guessing off.  The variables
+@code{dired-guess-shell-alist-user} and
+@code{dired-guess-shell-alist-default} will override these rules.
+@end defvar
+
 @defvar dired-guess-shell-alist-user
 If non-@code{nil}, this variable specifies the user-defined alist of
 file regexps and their suggested commands.  These rules take
-precedence over the predefined rules in the variable
-@code{dired-guess-shell-alist-default} when
+precedence over the predefined rules in the variables
+@code{dired-guess-shell-alist-default} and
+@code{dired-guess-shell-alist-optional} when
 @code{dired-do-shell-command} is run).  The default is @code{nil}.
 
 Each element of the alist looks like
diff --git a/etc/NEWS b/etc/NEWS
index a79a5844a22..23c87ca5c8b 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -817,6 +817,10 @@ marked or clicked on files according to the OS 
conventions.  For
 example, on systems supporting XDG, this runs 'xdg-open' on the
 files.
 
+*** New variable 'dired-guess-shell-alist-optional'.
+It contains commands for external viewers and players for various media
+formats, moved to this list from 'dired-guess-shell-alist-default'.
+
 *** The default value of 'dired-omit-size-limit' was increased.
 After performance improvements to omitting in large directories, the new
 default value is 300k, up from 100k.  This means 'dired-omit-mode' will
diff --git a/lisp/dired-aux.el b/lisp/dired-aux.el
index d1d5ed9b144..83e71b644b8 100644
--- a/lisp/dired-aux.el
+++ b/lisp/dired-aux.el
@@ -868,8 +868,8 @@ In a noninteractive call (from Lisp code), you must specify
 the list of file names explicitly with the FILE-LIST argument, which
 can be produced by `dired-get-marked-files', for example.
 
-`dired-guess-shell-alist-default' and
-`dired-guess-shell-alist-user' are consulted when the user is
+`dired-guess-shell-alist-default', `dired-guess-shell-alist-optional'
+and `dired-guess-shell-alist-user' are consulted when the user is
 prompted for the shell command to use interactively.
 
 Also see the `dired-confirm-shell-command' variable."
@@ -1068,8 +1068,8 @@ Return the result of `process-file' - zero for success."
 ;; * `dired-guess-shell-command' calls `dired-guess-default' with list of
 ;;    marked files.
 ;;
-;; * Parse `dired-guess-shell-alist-user' and
-;;   `dired-guess-shell-alist-default' (in that order) for the first REGEXP
+;; * Parse `dired-guess-shell-alist-user', `dired-guess-shell-alist-default',
+;;   `dired-guess-shell-alist-optional' (in that order) for the first REGEXP
 ;;   that matches the first file in the file list.
 ;;
 ;; * If the REGEXP matches all the entries of the file list then evaluate
@@ -1219,28 +1219,10 @@ Return the result of `process-file' - zero for success."
                   " " dired-guess-shell-znew-switches))
    '("\\.pod\\'" "perldoc" "pod2man * | nroff -man")
 
-   '("\\.dvi\\'" "xdvi" "dvips")       ; preview and printing
-   '("\\.au\\'" "play")                        ; play Sun audiofiles
-   '("\\.mpe?g\\'\\|\\.avi\\'" "xine -p")
-   '("\\.ogg\\'" "ogg123")
-   '("\\.mp3\\'" "mpg123")
-   '("\\.wav\\'" "play")
    '("\\.uu\\'" "uudecode")            ; for uudecoded files
-   '("\\.hqx\\'" "mcvert")
    '("\\.sh\\'" "sh")                  ; execute shell scripts
-   '("\\.xbm\\'" "bitmap")             ; view X11 bitmaps
-   '("\\.gp\\'" "gnuplot")
-   '("\\.p[bgpn]m\\'" "xloadimage")
-   '("\\.gif\\'" "xloadimage")         ; view gif pictures
-   '("\\.tif\\'" "xloadimage")
-   '("\\.png\\'" "display")            ; xloadimage 4.1 doesn't grok PNG
-   '("\\.jpe?g\\'" "xloadimage")
-   '("\\.fig\\'" "xfig")               ; edit fig pictures
-   '("\\.out\\'" "xgraph")             ; for plotting purposes.
    '("\\.tex\\'" "latex" "tex")
    '("\\.texi\\(nfo\\)?\\'" "makeinfo" "texi2dvi")
-   '("\\.pdf\\'" "xpdf")
-   '("\\.doc\\'" "antiword" "strings")
    '("\\.rpm\\'" "rpm -qilp" "rpm -ivh")
    '("\\.dia\\'" "dia")
    '("\\.mgp\\'" "mgp")
@@ -1269,7 +1251,37 @@ Return the result of `process-file' - zero for success."
 
    '("\\.sign?\\'" "gpg --verify"))
   "Default alist used for shell command guessing.
-See `dired-guess-shell-alist-user'.")
+See also `dired-guess-shell-alist-optional' and
+`dired-guess-shell-alist-user'.")
+
+(defvar dired-guess-shell-alist-optional
+  (list
+   '("\\.dvi\\'" "xdvi" "dvips")       ; preview and printing
+   '("\\.au\\'" "play")                        ; play Sun audiofiles
+   '("\\.mpe?g\\'\\|\\.avi\\'" "xine -p")
+   '("\\.ogg\\'" "ogg123")
+   '("\\.mp3\\'" "mpg123")
+   '("\\.wav\\'" "play")
+   '("\\.hqx\\'" "mcvert")
+   '("\\.xbm\\'" "bitmap")             ; view X11 bitmaps
+   '("\\.gp\\'" "gnuplot")
+   '("\\.p[bgpn]m\\'" "xloadimage")
+   '("\\.gif\\'" "xloadimage")         ; view gif pictures
+   '("\\.tif\\'" "xloadimage")
+   '("\\.png\\'" "display")            ; xloadimage 4.1 doesn't grok PNG
+   '("\\.jpe?g\\'" "xloadimage")
+   '("\\.fig\\'" "xfig")               ; edit fig pictures
+   '("\\.out\\'" "xgraph")             ; for plotting purposes.
+   '("\\.pdf\\'" "xpdf")
+   '("\\.doc\\'" "antiword" "strings"))
+  "Optional alist used for shell command guessing.
+Unlike `dired-guess-shell-alist-default' that contains mostly the
+standard commands that handle the files with corresponding extensions
+such as the `tar' command handling the files with the `.tar' extension,
+this list contains the commands such as media players and viewers
+that don't exist on many systems where other alternatives are available.
+
+See also `dired-guess-shell-alist-user'.")
 
 (defun dired-guess-default (files)
   "Return a shell command, or a list of commands, appropriate for FILES.
@@ -1289,7 +1301,8 @@ See `dired-guess-shell-alist-user'."
                                       (string-match-p (car elem) file))
                                     files))
                                  (append dired-guess-shell-alist-user
-                                         dired-guess-shell-alist-default)))
+                                         dired-guess-shell-alist-default
+                                         dired-guess-shell-alist-optional)))
              nil)))))
     (if (length= programs 1)
         (car programs)
@@ -1323,13 +1336,21 @@ See `dired-guess-shell-alist-user'."
       (if (equal val "") default val))))
 
 (defcustom shell-command-guess-functions
-  '(shell-command-guess-dired)
+  '(shell-command-guess-dired-optional
+    shell-command-guess-mailcap
+    shell-command-guess-xdg
+    shell-command-guess-dired-default
+    shell-command-guess-dired-user)
   "List of functions that guess shell commands for files.
 Each function receives a list of commands and a list of file names
 and should return the same list of commands with changes
-such as added new commands."
+such as new commands added to the beginning of the list.
+In this case the commands from the last entry
+will be at the top of the resulted list."
   :type '(repeat
-          (choice (function-item shell-command-guess-dired)
+          (choice (function-item shell-command-guess-dired-user)
+                  (function-item shell-command-guess-dired-default)
+                  (function-item shell-command-guess-dired-optional)
                   (function-item shell-command-guess-mailcap)
                   (function-item shell-command-guess-xdg)
                   (function-item shell-command-guess-open)
@@ -1350,9 +1371,29 @@ after adding own commands to the composite list."
                         nil))
     commands))
 
-(defun shell-command-guess-dired (commands files)
-  "Populate COMMANDS using `dired-guess-default'."
-  (append (ensure-list (dired-guess-default files)) commands))
+(defun shell-command-guess-dired-user (commands files)
+  "Populate COMMANDS using `dired-guess-shell-alist-user'.
+This excludes `dired-guess-shell-alist-default' and
+`dired-guess-shell-alist-optional'."
+  (let ((dired-guess-shell-alist-default nil)
+        (dired-guess-shell-alist-optional nil))
+    (append (ensure-list (dired-guess-default files)) commands)))
+
+(defun shell-command-guess-dired-default (commands files)
+  "Populate COMMANDS using `dired-guess-shell-alist-default'.
+This excludes `dired-guess-shell-alist-user' and
+`dired-guess-shell-alist-optional'."
+  (let ((dired-guess-shell-alist-user nil)
+        (dired-guess-shell-alist-optional nil))
+    (append (ensure-list (dired-guess-default files)) commands)))
+
+(defun shell-command-guess-dired-optional (commands files)
+  "Populate COMMANDS using `dired-guess-shell-alist-optional'.
+This excludes `dired-guess-shell-alist-user' and
+`dired-guess-shell-alist-default'."
+  (let ((dired-guess-shell-alist-user nil)
+        (dired-guess-shell-alist-default nil))
+    (append (ensure-list (dired-guess-default files)) commands)))
 
 (declare-function mailcap-file-default-commands "mailcap" (files))
 
diff --git a/lisp/dired.el b/lisp/dired.el
index 21085de97f2..2b1db9f6e31 100644
--- a/lisp/dired.el
+++ b/lisp/dired.el
@@ -443,8 +443,9 @@ is anywhere on its Dired line, except the beginning of the 
line."
 
 (defcustom dired-guess-shell-alist-user nil
   "User-defined alist of rules for suggested commands.
-These rules take precedence over the predefined rules in the variable
-`dired-guess-shell-alist-default' (to which they are prepended).
+These rules take precedence over the predefined rules in the variables
+`dired-guess-shell-alist-default' and `dired-guess-shell-alist-optional'
+\(to which they are prepended).
 
 Each element of this list looks like