bug#26205: Unhappy with deprecating GREP_OPTIONS

[Paul Eggert]

On 11/07/2017 01:00 PM, Ankeet wrote:
> grep should test for an interactive shell before parsing GREP_OPTIONS. [There 
> are a number of methods outlined in the man 
> page](http://www.tldp.org/LDP/abs/html/intandnonint.html).

Most of those methods would not work for grep, which is not a shell 
script. The only exception (testing whether stdin is a terminal) would 
run afoul of the GNU coding standards, which say that the behavior of a 
program should not depend on whether standard input or output is a 
terminal device. See:

https://www.gnu.org/prep/standards/html_node/User-Interfaces.html

Although we stretch those rules occasionally, stretching does not seem 
advisable here.