bug#12915: 24.2.50; Visiting a file via drag-and-drop should add it to the history ofvisited files

[Juri Linkov]

> `file-name-history' was designed to be augmented by `read-file-name', 
> whenever a
> file name is input.  That includes commands that do not display/visit the 
> file.
> This way of interactively choosing files should not be ignored, just because
> someone finds an easy way to hook history augmentation into file-buffer 
> display.

A new variable (e.g. `file-name-history-variable') could be introduced
to hold the name of the history variable.  The default would be the
currently existing `file-name-history'.  And the other possible value
would be a new history variable (e.g. `file-name-extended-history')
that will collect all visited/displayed file names like:

(defvar file-name-history nil
  "History list of file names entered in the minibuffer.")

(defvar file-name-extended-history nil
  "History list of files visited/displayed in the current session.")

(defcustom file-name-history-variable 'file-name-history
  "History list to use in the minibuffer that reads a file name.
The value of this variable should be a symbol; that symbol
is used as a variable to hold a history list for the file names."
  :group 'files
  :type 'symbol)

Then the users would be able to customize it to `file-name-extended-history':

(custom-set-variables
 '(file-name-history-variable file-name-extended-history))