Add commands to run shell commands in project root

* lisp/progmodes/project.el (project-async-shell-command)
(project-shell-command): New commands to run 'async-shell-command'
and 'shell-command' in project's root directory.
(project-prefix-map): Bind commands to '!' and '&'.
* doc/emacs/maintaining.texi (Project File Commands): Document the
new commands.
* etc/NEWS: Announce the new commands.

doc/emacs/maintaining.texi

@@ -1693,6 +1693,12 @@ Start Eshell in the current project's root directory
 @item C-x p c
 Run compilation in the current project's root directory
 (@code{project-compile}).
+@item C-x p !
+Run shell command in the current project's root directory
+(@code{project-shell-command}).
+@item C-x p &
+Run shell command asynchronously in the current project's root
+directory (@code{project-async-shell-command}).
 @end table
 
   Emacs provides commands for handling project files conveniently.
@@ -1770,6 +1776,14 @@ directory.  @xref{Top,Eshell,Eshell, eshell, Eshell: The Emacs Shell}.
   The command @kbd{C-x p c} (@code{project-compile}) runs compilation
 (@pxref{Compilation}) in the current project's root directory.
 
+@findex project-shell-command
+  The command @kbd{C-x p !} (@code{project-shell-command}) runs
+@code{shell-command} in the current project's root directory.
+
+@findex project-async-shell-command
+  The command @kbd{C-x p &} (@code{project-async-shell-command}) runs
+@code{async-shell-command} in the current project's root directory.
+
 @node Project Buffer Commands
 @subsection Project Commands That Operate on Buffers
 

etc/NEWS

@@ -778,6 +778,11 @@ directory.
 This command lets you "switch" to another project and run a project
 command chosen from a dispatch menu.
 
++++
+*** New commands 'project-shell-command' and 'project-async-shell-command'.
+These commands run 'shell-command' and 'async-shell-command' in a
+project's root directory, respectively.
+
 +++
 *** New user option 'project-list-file'.
 

lisp/progmodes/project.el

@@ -581,6 +581,8 @@ DIRS must contain directory names."
 ;;;###autoload
 (defvar project-prefix-map
   (let ((map (make-sparse-keymap)))
+    (define-key map "!" 'project-shell-command)
+    (define-key map "&" 'project-async-shell-command)
     (define-key map "f" 'project-find-file)
     (define-key map "F" 'project-or-external-find-file)
     (define-key map "b" 'project-switch-to-buffer)
@@ -882,6 +884,20 @@ if one already exists."
         (pop-to-buffer eshell-buffer)
       (eshell t))))
 
+;;;###autoload
+(defun project-async-shell-command ()
+  "Run `async-shell-command' in the current project's root directory."
+  (interactive)
+  (let ((default-directory (project-root (project-current t))))
+    (call-interactively #'async-shell-command)))
+
+;;;###autoload
+(defun project-shell-command ()
+  "Run `shell-command' in the current project's root directory."
+  (interactive)
+  (let ((default-directory (project-root (project-current t))))
+    (call-interactively #'shell-command)))
+
 (declare-function fileloop-continue "fileloop" ())
 
 ;;;###autoload