Bind : to run Git commands directly.

I chose : as the binding for similarity with M-:.

magit.el

@@ -1448,6 +1448,7 @@ FUNC should leave point at the end of the modified region"
     (define-key map (kbd "G") 'magit-refresh-all)
     (define-key map (kbd "?") 'magit-describe-item)
     (define-key map (kbd "!") 'magit-shell-command)
+    (define-key map (kbd ":") 'magit-git-command)
     (define-key map (kbd "RET") 'magit-visit-item)
     (define-key map (kbd "SPC") 'magit-show-item-or-scroll-up)
     (define-key map (kbd "DEL") 'magit-show-item-or-scroll-down)
@@ -2965,6 +2966,23 @@ Uncomitted changes in both working tree and staging area are lost.
 	(magit-process-popup-time 0))
     (magit-run* args nil nil nil t)))
 
+(defun magit-git-command (command)
+  "Perform arbitrary Git COMMAND.
+
+Similar to `magit-shell-command', but involves slightly less
+typing and automatically refreshes the status buffer."
+  (interactive "sgit ")
+  (require 'pcomplete)
+  (let ((args (car (with-temp-buffer
+		     (insert command)
+		     (pcomplete-parse-buffer-arguments))))
+	(magit-process-popup-time 0))
+    (magit-with-refresh
+      (magit-run* (append (cons magit-git-executable
+                                magit-git-standard-options)
+                          args)
+                  nil nil nil t))))
+
 (defun magit-read-remote (prompt def)
   (funcall magit-completing-read (if def
 		       (format "%s (default %s): " prompt def)

magit.texi

@@ -49,6 +49,7 @@ as an extension to Emacs.
 * Rewriting::                   
 * Pushing and Pulling::         
 * Interfacing with Subversion::  
+* Using Git Directly::
 @end menu
 
 @node Introduction
@@ -683,4 +684,12 @@ limited to the path of the remote Subversion repository. With a prefix
 (@kbd{C-u N f} the user will also be prompted for a branch to search
 in.
 
+@node Using Git Directly
+@chapter Using Git Directly
+
+For situations when Magit doesn't do everything you need, you can run
+raw Git commands using @kbd{:}.  This will prompt for a Git command, run
+it, and refresh the status buffer.  The output can be viewed by typing
+@kbd{$}.
+
 @bye