Make magit-status prompt less.

* magit.el (magit-status): Only read the top directory with e prefix
argument or when we are not inside a Git repository.
* magit.texi, NEWS: Document the new behavior.

NEWS

@@ -14,6 +14,9 @@ Changes in magit 0.7:
   'L' shows a more verbose log.  Use the prefix arg to specify the
   range of the log.
 
+* M-x magit-status doesn't prompt anymore for a directory when invoked
+  from within a Git repository.  Use C-u to force a prompt.
+
 * Magit works better with oldish Gits that don't understand "--graph"
   for example.
 

magit.el

@@ -1584,7 +1584,9 @@ in log buffer."
 	  (magit-insert-unpushed-commits remote branch))))))
 
 (defun magit-status (dir)
-  (interactive (list (magit-read-top-dir)))
+  (interactive (list (or (and (not current-prefix-arg)
+			      (magit-get-top-dir default-directory))
+			 (magit-read-top-dir))))
   (if magit-save-some-buffers
       (save-some-buffers (eq magit-save-some-buffers 'dontask)))
   (let* ((topdir (magit-get-top-dir dir))

magit.texi

@@ -100,6 +100,11 @@ Running @kbd{M-x magit-status} displays the main interface of Magit,
 the status buffer.  You can have multiple status buffers active at the
 same time, each associated with its own Git repository.
 
+When invoking @kbd{M-x magit-status} from within a Git repository, it
+will switch to the status buffer of that repository.  Otherwise, it
+will prompt for a directory.  With a rpefix argument, it will always
+prompt.
+
 You need to explicitly refresh the status buffer when you have made
 changes to the repository from outside of Emacs.  You can type @kbd{g}
 in the status buffer itself, or just use @kbd{M-x magit-status}