[ESS] indentation when using = rather than <-

[Tim Hesterberg]

I'm trying to move away from using _ for assignment, but
rather than <- I want to use =
(for a number of reasons, the biggest of which is that <- is
a barrier to new users adopting the S language).

Unfortunately, ESS does not treat <- and = the same for
indentation (example below).

How would I get ESS to treat "=" the same as "<-" for purposes
of indentation?

I tried adding "=" to the ess-S-assign-ops variable, but that
didn't seem to affect indentation.  There is a comment in the
definition of the variable suggesting the omission of "="
is intentional, so I'm wondering about possible negative ramifications
of modifying the ESS code to make indentation work as I like.

--------------------------------------------------
Example:

If I create the following functions with
no initial blanks, then run ess-indent-exp from the beginning
of each function, I get the following; I'd like indenting the
second version to be similar to indenting the first.

f <- function(x){
  a
  if(b){
    c <- foo1(x = 2, y = 3, foo2(z = mean(x)),
	      a, b = 5)
    for(i in 1:n)
      d[i] <- foo3(z, foo4(a = 3,
			   b =
			   5, c, foo5(d)))
  }
}

f = function(x){
  a
  if(b){
    c = foo1(x = 2, y = 3, foo2(z = mean(x)),
      a, b = 5)
    for(i in 1:n)
      d[i] = foo3(z, foo4(a = 3,
	 b =
	 5, c, foo5(d)))
  }
}