bug#30503: 27.0.50; allow hiding M-x grep command line

[charles@aurox.ch (Charles A. Roelli)]

> From: Juri Linkov <juri@linkov.net>
> Cc: charles@aurox.ch,  30503@debbugs.gnu.org
> Organization: LINKOV.NET
> Date: Thu, 22 Feb 2018 23:51:57 +0200
> 
> >> > In any case, this needs to be documented in NEWS and the manual, I
> >> > think.
> >>
> >> Changes to NEWS are added in this patch without “---” to not forget
> >> to document it in the manual before the release of Emacs 27.1.
> >
> > Thanks, but I'd prefer that we update the manual as part of this
> > changeset.  Leaving manuals outdated tends to create a very large job
> > to be done before a pretest can be released, which I find to be
> > sub-optimal.  It also prevents users who track the development from
> > finding possible mistakes in the manual, because they don't have
> > enough time to d that before an official release.
> >
> > Would you like to make the corrections in the manual as well?
> 
> Pushed to master together with the corrections in the manual.
> 
> Charles, please update your patch from master, you have many
> good improvements in your previous patch.

Thanks for adding this feature.  Here's the change that implements a
toggling command.

diff --git a/doc/emacs/building.texi b/doc/emacs/building.texi
index 8e2fdf1..eee6329 100644
--- a/doc/emacs/building.texi
+++ b/doc/emacs/building.texi
@@ -435,13 +435,16 @@ Grep Searching
 by various version control systems.
 
 @vindex grep-find-hide
+@findex grep-find-toggle-abbreviation
   By default, the shell commands constructed for @code{lgrep},
 @code{rgrep}, and @code{zgrep} are abbreviated for display by
 concealing the part that contains a long list of files and directories
 to ignore.  You can reveal the concealed part by clicking on the
-button with ellipsis, which represents them.  To disable this
-abbreviation of the shell commands, customize the option
-@code{grep-find-hide} to a @code{nil} value.
+button with ellipsis, which represents them.  You can also
+interactively toggle viewing the concealed part by typing @kbd{M-x
+grep-find-toggle-abbreviation}.  To disable this abbreviation of the
+shell commands, customize the option @code{grep-find-hide} to a
+@code{nil} value.
 
 @node Flymake
 @section Finding Syntax Errors On The Fly
diff --git a/etc/NEWS b/etc/NEWS
index 596adf8..166b419 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -203,6 +203,8 @@ by default.
 that contains a list of ignored directories and files.
 Clicking on the button with ellipsis unhides the truncated part.
 This truncation can be disabled by the new option 'grep-find-hide'.
+The new command 'grep-find-toggle-abbreviation' toggles the hiding
+interactively.
 
 ** ERT
 
diff --git a/lisp/progmodes/grep.el b/lisp/progmodes/grep.el
index 9b2c6f1..67139b4 100644
--- a/lisp/progmodes/grep.el
+++ b/lisp/progmodes/grep.el
@@ -437,7 +437,9 @@ grep-find-hide
   "If non-nil, hide part of rgrep/lgrep/zrgrep command line.
 The hidden part contains a list of ignored directories and files.
 Clicking on the button-like ellipsis unhides the abbreviated part
-and reveals the entire command line."
+and reveals the entire command line.  The visibility of the
+abbreviated part can also be toggled with
+`grep-find-toggle-abbreviation'."
   :type 'boolean
   :version "27.1"
   :group 'grep)
@@ -446,11 +448,11 @@ grep-find-hide-properties
   (let ((ellipsis (if (char-displayable-p ?…) "[…]" "[...]"))
         (map (make-sparse-keymap)))
     (define-key map [down-mouse-2] 'mouse-set-point)
-    (define-key map [mouse-2] 'grep-find-show)
-    (define-key map "\C-m" 'grep-find-show)
+    (define-key map [mouse-2] 'grep-find-toggle-abbreviation)
+    (define-key map "\C-m" 'grep-find-toggle-abbreviation)
     `(face nil display ,ellipsis mouse-face highlight
       help-echo "RET, mouse-2: show unabbreviated command"
-      keymap ,map))
+      keymap ,map abbreviated-command t))
   "Properties of button-like ellipsis on part of rgrep command line.")
 
 (defvar grep-mode-font-lock-keywords
@@ -476,10 +478,12 @@ grep-mode-font-lock-keywords
              `(face nil display ,(match-string 2)))))
      ;; Hide excessive part of rgrep command
      ("^find \\(\\. -type d .*\\\\)\\)"
-      (1 (when grep-find-hide grep-find-hide-properties)))
+      (1 (if grep-find-hide grep-find-hide-properties
+           '(face nil abbreviated-command t))))
      ;; Hide excessive part of lgrep command
      ("^grep \\( *--exclude.*--exclude[^ ]+\\)"
-      (1 (when grep-find-hide grep-find-hide-properties))))
+      (1 (if grep-find-hide grep-find-hide-properties
+           '(face nil abbreviated-command t)))))
    "Additional things to highlight in grep output.
 This gets tacked on the end of the generated expressions.")
 
@@ -1195,23 +1199,19 @@ rgrep-default-command
                  (shell-quote-argument ")")
                  " -prune -o ")))))
 
-(defun grep-find-show ()
-  "Show the hidden part of rgrep/lgrep/zrgrep command line."
+(defun grep-find-toggle-abbreviation ()
+  "Toggle showing the hidden part of rgrep/lgrep/zrgrep command line."
   (interactive)
-  (when (get-text-property (point) 'display)
-    (let ((beg (or (previous-single-property-change
-                    (min (point-max) (1+ (point))) 'display)
-                   (point)))
-          (end (or (next-single-property-change
-                    (point) 'display)
-                   (point)))
-          (inhibit-modification-hooks t)
-          (inhibit-read-only t)
-	  (buffer-undo-list t)
-	  (modified (buffer-modified-p)))
-      (remove-list-of-text-properties
-       beg end '(display help-echo mouse-face help-echo keymap))
-      (set-buffer-modified-p modified))))
+  (with-silent-modifications
+    (let* ((beg (next-single-property-change (point-min) 'abbreviated-command))
+           (end (when beg
+                  (next-single-property-change beg 'abbreviated-command))))
+      (if end
+          (if (get-text-property beg 'display)
+              (remove-list-of-text-properties
+               beg end '(display help-echo mouse-face help-echo keymap))
+            (add-text-properties beg end grep-find-hide-properties))
+        (user-error "No abbreviated part to hide/show")))))
 
 ;;;###autoload
 (defun zrgrep (regexp &optional files dir confirm template)