[ESS] Setting paths to R versions in different directories

[Stephen Eglen]

> I have just got a new system and got R devel installed from
> source in ~/bin/R-patched/, then I
>
>   cd ~/bin && ln -sf R-patched/bin/R R-latest
>
> and re-started Emacs. Then M-x R- TAB, no R-latest in there.
>
> So, R-latest should have been created and should have been in the
> completion list, right?

No (close, but no).  I hope

cd ~/bin && ln -sf R-patched/bin/R R-patched-latest

would work; see:
----------------------------------------------------------------------
ess-r-versions is a variable defined in `ess-r-d.el'.
Its value is ("R-1" "R-2" "R-3" "R-devel" "R-patched" "R32" "R64")

Documentation:
List of partial strings for versions of R to access within ESS.
Each string specifies the start of a filename.  If a filename
beginning with one of these strings is found on `exec-path', a M-x
command for that version of R is made available.  For example, if the
file "R-1.8.1" is found and this variable includes the string
"R-1", a function called `M-x R-1.8.1' will be available to run that
version of R.
If duplicate versions of the same program are found (which happens if
the same path is listed on `exec-path' more than once), they are
ignored by calling `ess-uniq-list'.
Set this variable to nil to disable searching for other versions of R.
If you set this variable, you need to restart Emacs (and set this variable
before ess-site is loaded) for it to take effect.