Add `r'/`l' grep command history commands

* doc/emacs/building.texi (Grep Searching): Mention the
`r'/`l' commands.

* lisp/progmodes/grep.el (grep-forward-history): New command.
(grep-backward-history): Ditto.
(grep--save-buffers): New function.
(grep): Use it to record the history.
(grep--command-history, grep--history-inhibit)
(grep--history-place): New internal variables for the grep
history (bug#22627).

3 files changed, 58 insertions, 1 deletions

diff --git a/doc/emacs/building.texi b/doc/emacs/building.texi
index 03fa0ed83b2..059c7cae89c 100644
--- a/doc/emacs/building.texi
+++ b/doc/emacs/building.texi
@@ -390,6 +390,13 @@ is called with the file name as the parameter and should return
 non-nil if the buffer is to be saved), and any other non-@code{nil}
 value means that all buffers should be saved without asking.
 
+  In addition to the normal compilation mode commands (for
+next/previous match and so on), two additional commands are available
+for accessing the @command{grep} command history.  @kbd{l}
+(@code{grep-backward-history}) will re-run successively the previous
+@command{grep} commands, and @kbd{r} (@code{grep-forward-history}
+will go ``forward'' in the command history.
+
 @findex grep-find
 @findex find-grep
   The command @kbd{M-x grep-find} (also available as @kbd{M-x
diff --git a/etc/NEWS b/etc/NEWS
index d878228720e..88e101ee0f0 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -57,6 +57,10 @@ has been added.  They are: 'file-attribute-type',
 ** The new function 'buffer-hash' has been added, and can be used to
 compute a fash, non-consing hash of the contents of a buffer.
 
++++
+** The grep mode now has a command history that you can access via the
+`r' and `l' commands.
+
 ---
 ** 'fill-paragraph' no longer marks the buffer as changed unless it
 actually changed something.
@@ -1807,6 +1811,7 @@ behavior, set 'diff-switches' to '-c'.
 dynamically.  Any third-party code that changes these templates should
 be updated accordingly.
 
++++
 ** The grep/rgrep/lgrep functions will now ask about saving files
 before running.  This is controlled by the 'grep-save-buffers'
 variable.
diff --git a/lisp/progmodes/grep.el b/lisp/progmodes/grep.el
index 2b44b58f245..7ce787e7284 100644
--- a/lisp/progmodes/grep.el
+++ b/lisp/progmodes/grep.el
@@ -271,6 +271,8 @@ See `compilation-error-screen-columns'"
     (define-key map "{" 'compilation-previous-file)
     (define-key map "}" 'compilation-next-file)
     (define-key map "\t" 'compilation-next-error)
+    (define-key map "r" 'grep-forward-history)
+    (define-key map "l" 'grep-backward-history)
     (define-key map [backtab] 'compilation-previous-error)
 
     ;; Set up the menu-bar
@@ -309,6 +311,12 @@ See `compilation-error-screen-columns'"
     (define-key map [menu-bar grep compilation-next-error]
       '(menu-item "Next Match" next-error
                   :help "Visit the next match and corresponding location"))
+    (define-key map [menu-bar grep grep-backward-history]
+      '(menu-item "Previous Command" grep-backward-history
+                  :help "Run the previous grep command from the command history"))
+    (define-key map [menu-bar grep grep-forward-history]
+      '(menu-item "Next Command" grep-forward-history
+                  :help "Run the next grep command from the command history"))
     map)
   "Keymap for grep buffers.
 `compilation-minor-mode-map' is a cdr of this.")
@@ -744,6 +752,43 @@ This function is called from `compilation-filter-hook'."
        grep-error-screen-columns)
   (add-hook 'compilation-filter-hook 'grep-filter nil t))
 
+(defvar grep--command-history nil)
+(defvar grep--history-inhibit nil)
+(defvar grep--history-place 0)
+
+(defun grep--save-history (command)
+  (unless grep--history-inhibit
+    (push (cons default-directory command) grep--command-history)
+    (setq grep--history-place 0)
+    ;; Don't let the history grow without bounds.
+    (when (> (length grep--command-history) 100)
+      (setcdr (nthcdr 100 grep--command-history) nil))))
+
+(defun grep-forward-history ()
+  "Go to the next result in the grep command history.
+Also see `grep-backward-history'."
+  (interactive)
+  (let ((elem (and (> grep--history-place 0)
+                   (nth (1- grep--history-place) grep--command-history)))
+        (grep--history-inhibit t))
+    (unless elem
+      (error "Nothing further in the command history"))
+    (cl-decf grep--history-place)
+    (let ((default-directory (car elem)))
+      (grep (cdr elem)))))
+
+(defun grep-backward-history ()
+  "Go to the previous result in the grep command history.
+Also see `grep-forward-history'."
+  (interactive)
+  (let ((elem (nth (1+ grep--history-place) grep--command-history))
+        (grep--history-inhibit t))
+    (unless elem
+      (error "Nothing further in the command history"))
+    (cl-incf grep--history-place)
+    (let ((default-directory (car elem)))
+      (grep (cdr elem)))))
+
 (defun grep--save-buffers ()
   (when grep-save-buffers
     (save-some-buffers (and (not (eq grep-save-buffers 'ask))
@@ -780,7 +825,7 @@ list is empty)."
                                  (if current-prefix-arg default grep-command)
                                  'grep-history
                                  (if current-prefix-arg nil default))))))
-
+  (grep--save-history command-args)
   (grep--save-buffers)
   ;; Setting process-setup-function makes exit-message-function work
   ;; even when async processes aren't supported.