bug#2397: 23.0.90; grep no longer highlights the match

[Drew Adams]

> > grep -nH -e echo $SHELL
> > Binary file C:/cygwin/bin/bash.exe matches
> >
> > Looks like bash to me. And it's always acted like bash, AFAICT.
> 
> > That gives this:
> >
> > grep -nH -e echo $TERM
> > grep: emacs-grep: No such file or directory
> 
> Actually I meant removing the default input (the "grep -nH -e" part)
> completely, and replacing it with these commands.  So more precise
> recipes are:
> 
> `M-x grep RET C-a C-k set RET'

Here:

...
SHELL=C:/cygwin/bin/bash.exe
...
TERM=emacs-grep

> `M-x grep RET C-a C-k echo $TERM RET'

echo $TERM
emacs-grep

> But anyway I see that your $SHELL is "bash.exe" and $TERM is 
> "emacs-grep".
> 
> Could you also try running grep from Bash (not from Emacs) 
> with options "--color=always" and "--color=auto" and see whether
> it outputs highlighting sequences for both cases in a standalone
> shell?

Yes, both produce the highlighting.
It is apparently only in Emacs that --color=auto does not work.