Re: [PATCH] dist-xz: don't hard-code -9: honor setting of XZ_OPT

[Jim Meyering]

Ralf Wildenhues wrote:
> * Jim Meyering wrote on Sun, Oct 03, 2010 at 12:35:57PM CEST:
>> * lib/am/distdir.am (dist-xz): Do not hard-code xz's -9: that
>> made it impossible to override.  Instead, use its XZ_OPT envvar,
>> defaulting to -9 if not defined.  Thus no change in behavior
>> when XZ_OPT is not set, and now, this rule honors the setting
>> of that envvar when it is set.  Suggested by Lasse Collin.
>
> Thanks.  A more general fix for all dist-* compressors, with hopefully
> as uniform naming scheme as is possible throughout, and autoconf.texi

Hi Ralf,

automake.texi, I presume.

> and NEWS update, was already on my list of things to do.  (There are
> some prior bug reports too.)

The name I used there, XZ_OPT, is dictated by the tool.  An alternative
is to invoke xz with no explicit XZ_OPT setting, but that would result
in a semantic change: using the default compression level of -7 rather
than what was hard-coded as -9.  Perhaps that would be better, because
some people have complained that using -9 makes it harder to decompress
(requires more memory) on extremely low-memory (embedded) systems.

Hence, my using an explicit XZ_OPT setting served three purposes:
- preserved the existing -9 (perhaps not desirable)
- allowed an override
- documented in the Makefile that xz's behavior can be overridden
    through that envvar.

There is no point in changing lzma, since it's deprecated.
bzip2 and lzip hard-code the -9, just like xz does/did.
bzip2 honors BZIP2, but lzip appears to honor no envvar.
gzip doesn't hard-code a compression level and besides,
it already honors the $(GZIP_ENV) makefile variable.

With all that, trying to make an across-the-board, consistent change
appears to be a lost cause.

As a half measure, I could change bzip2 in the same way as xz, but
hesitated to do even that, since I feel that bzip2 has been subsumed.
Tell me what you'd like.

> If you can provide anything, be my guest, otherwise I'll try to either
> fix things within a week or so, or take your patch for now.  Is that OK?