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

[Juri Linkov]

>> > Could we provide an option to hide the barrage of ignored directories
>> > and files?  It might also be worth adding a text button or keybinding
>> > to toggle their visibility interactively.
>>
>> Yes, this is a real problem.  Even though I set truncate-lines to t,
>> often there is a need to see grep switches at the end of the
>> command line.  So there is a patch to hide uninteresting parts
>> under a button like is used to hide part of output by
>> elisp-last-sexp-toggle-display.  It supports rgrep, lgrep and zrgrep.
>
> Thanks, but where's the option to hide the long list?  It looks like
> this patch changes the behavior unconditionally, and makes it
> strikingly different from the previous behavior.

Like there is the option eval-expression-print-length to disable hiding
of long output from eval-last-sexp, we could add a similar option here
as well.

> 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.

diff --git a/etc/NEWS b/etc/NEWS
index 71569c9..0ba369e7 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -158,6 +158,13 @@ by default.
 
 ** Gamegrid
 
+** grep
+
+*** rgrep, lgrep and zrgrep now hide part of the command line
+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 'rgrep-command-hide'.
+
 ** ERT
 
 +++
diff --git a/lisp/progmodes/grep.el b/lisp/progmodes/grep.el
index 14e251e..d249c51 100644
--- a/lisp/progmodes/grep.el
+++ b/lisp/progmodes/grep.el
@@ -433,6 +433,26 @@ grep-mode-line-matches
                       help-echo "Number of matches so far")
     "]"))
 
+(defcustom rgrep-command-hide t
+  "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."
+  :type 'boolean
+  :version "27.1"
+  :group 'grep)
+
+(defvar rgrep-command-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] 'rgrep-command-show)
+    (define-key map "\C-m" 'rgrep-command-show)
+    `(face nil display ,ellipsis mouse-face highlight
+      help-echo "RET, mouse-2: show unabbreviated command"
+      keymap ,map))
+  "Properties of button-like ellipsis on part of rgrep command line.")
+
 (defvar grep-mode-font-lock-keywords
    '(;; Command output lines.
      (": \\(.+\\): \\(?:Permission denied\\|No such \\(?:file or 
directory\\|device or address\\)\\)$"
@@ -452,7 +472,13 @@ grep-mode-font-lock-keywords
      ;; "filename=linenumber=" for lines with function names in "git grep -p".
      ("^.+?\\([-=\0]\\)[0-9]+\\([-=]\\).*\n" (0 grep-context-face)
       (1 (if (eq (char-after (match-beginning 1)) ?\0)
-             `(face nil display ,(match-string 2))))))
+             `(face nil display ,(match-string 2)))))
+     ;; Hide excessive part of rgrep command
+     ("^find \\(\\. -type d .*\\\\)\\)"
+      (1 (when rgrep-command-hide rgrep-command-hide-properties)))
+     ;; Hide excessive part of lgrep command
+     ("^grep \\( *--exclude.*--exclude[^ ]+\\)"
+      (1 (when rgrep-command-hide rgrep-command-hide-properties))))
    "Additional things to highlight in grep output.
 This gets tacked on the end of the generated expressions.")
 
@@ -1166,6 +1192,24 @@ rgrep-default-command
                  (shell-quote-argument ")")
                  " -prune -o ")))))
 
+(defun rgrep-command-show ()
+  "Show 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))))
+
 ;;;###autoload
 (defun zrgrep (regexp &optional files dir confirm template)
   "Recursively grep for REGEXP in gzipped FILES in tree rooted at DIR.