[ESS] ESS unable to find R on Linux when emacs started by opening a .R file

[Stephen Eglen]

> I've been re-setting up my laptop after upgrading my Fedora installation to
> Fedora 22. I run a locally built R (in ~/R/build/3.2-patched) with a sym
> link to the R executable located in ~/bin. I am using the github version of
> ESS (setup today).
>
> I can start R in a bash shell in the usual way (typing R), and from within
> Emacs shell after M-x shell. I can also do M-x R in a clean Emacs session
> (no files loaded into buffers). What is not working for me is starting R
> within Emacs via M-x R when I have a .R file open in the Emacs buffer.
> Instead I see "Searching for program: no such file or directory, R" after I
> accept the suggestion for the starting directory.
>
> Anyone know what is going on here and how to solve this issue?
>

Sounds odd!  What is the value of exec-path (C-h v RET exec-path RET)
once you start Emacs, and then after you have visited an .R buffer?