emacs 22 - regular-expression isearch on spaces extremely lenient

["Ken Manheimer" <ken.manheimer@gmail.com>]

i recently started noticing that emacs 22 regular expression isearches
do not treat spaces exactly - any number of spaces in your search will
map to any number, same or different, of spaces in the target.

for example:
 - copy this message into an empty buffer
 - postiong the cursor at the beginning of the buffer
 - start an isearch (Ctrl-s)
 - toggle it to a regexp-isearch (Meta-r)
 - enter three spaces
 - enter an "s"
when i do this, the cursor winds up positioned on the "s" at the
beginning of the third word in this message, "started".

i'm starting to realize that this behavior has been in emacs 22 for at
least a while, and is not in emacs 21.  can anyone tell me whether or
not it's deliberate, and what the rationale is?  (i started writing
this up as a bug for emacs-devel, but looking into isearch-search and
seeing that `search-spaces-regexp' is specifically set to the value of
`search-whitespace-regexp' is making me suspect that the behavior is a
deliberate design feature.  ?)
--
ken manheimer
ken.manheimer@gmail.com
http://myriadicity.net