bug#3424: align-regexp: Infinite loop with default regexp

[Teemu Likonen <tlikonen@iki.fi>]

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The align-regexp command enters infinite loop when it is used with the
default regexp and with REPEAT argument. It's seems to be because the
regexp \s-* matches also zero-length strings.

Steps to reproduce:

 1. Put the following line to the *scratch* buffer:

        foo bar

 2. Put the line inside a region

 3. Type command:

        C-u M-x align-regexp RET \(\s-*\) RET 1 RET 1 RET y

 4. Loop infinitely.


I suggest changing the default regexp to \(\s-+\), like the attached
patch illustrates.


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diff --git i/lisp/align.el w/lisp/align.el
index 0917e7d..ea36302 100644
--- i/lisp/align.el
+++ w/lisp/align.el
@@ -933,7 +933,7 @@ region, call `align-regexp' and type in that regular expression."
     (list (region-beginning) (region-end))
     (if current-prefix-arg
 	(list (read-string "Complex align using regexp: "
-			   "\\(\\s-*\\)")
+			   "\\(\\s-+\\)")
 	      (string-to-number
 	       (read-string
 		"Parenthesis group to modify (justify if negative): " "1"))
@@ -941,7 +941,7 @@ region, call `align-regexp' and type in that regular expression."
 	       (read-string "Amount of spacing (or column if negative): "
 			    (number-to-string align-default-spacing)))
 	      (y-or-n-p "Repeat throughout line? "))
-      (list (concat "\\(\\s-*\\)"
+      (list (concat "\\(\\s-+\\)"
 		    (read-string "Align regexp: "))
 	    1 align-default-spacing nil))))
   (let ((rule