bug#20104: [PATCH] gzip: make the GZIP env var obsolescent

[Paul Eggert]

Mark Adler wrote:
> You could allow only compression level options in the environment variable, 
> which I think was its main intent in the first place.

The documentation currently suggests using GZIP to specify -q, -v, and --name 
(-N), so it appears that this intent was lost long ago.

Allowing "harmless" options in GZIP raises the question: where does one draw the 
line between "harmless" and "harmful"?  Clearly options like -d and -t are 
typically harmful.  In contrast, -q, -v, -n, -N, and -1 through -9 might be 
harmless in many cases, though they could still cause problems in some.

Any rule that says that GZIP is OK for some options but not others would add 
some complexity to the spec, and would be confusing in the long run for users.

I'm inclined to implement your suggestion immediately (i.e., for the next 
release of gzip), while documenting that the GZIP environment variable is 
obsolescent and that we plan to remove it entirely later.  Following Jim's 
suggestion, gzip should exit with status 0 rather than status 2 when it warns 
about the nontrivial use of the GZIP environment variable.