[pacman-dev] Open up a place for BUILDENV extensions

[Que Quotion]

 >How exactly is this related to BUILDENV? This seems to be allowing 
arbitrary code to run before executing the build() function.

You can use the word "arbitrary" to make it sound like a bad idea if 
you like, but it very simply does for BUILDENV exactly what tidy.sh 
does for OPTIONS: allow for supplemental scripts to add to makepkg's 
functionality at this stage.

In fact, it does it in exactly the same way--because nearly all of this 
code was copied and pasted from tidy.sh.

Just as tidy.sh allows any kind of anything to be run, it could allow 
any bash script to be run here--but the intention is for scripts that 
serve build-environment altering functions to be run here (as the 
intention for tidy.sh is to run cleanup and compression scripts).

Your concern about cleanup seems misplaced. It will be up to the 
authors of supplemental scripts to make sure they work properly, and 
users who trust them to install and enable those features. This 
patch--in and of itself--will not cause the problems you are worried 
about.

 >This line does nothing, even if correctly spelled.

What is misspelled? This is intended to serve the same purpose as the 
same line serves in tidy.sh:

declare -a packaging_options tidy_remove tidy_modify

The tidy scripts have names like upx.sh, the buildenv_ext scripts will 
have names like svgo.sh; these variables store the names of those 
options as they will be known in makepkg(-optimize).conf.

 >Since nullglob isn't set, an empty directory will cause this to throw
an error about a missing file (as the glob will turn into a literal). As
there's no "buildenv_ext" files provided by makepkg, this means we error
by default.

That could be fixed very easily, but again: copy pasta from tidy.sh. If 
you have a problem with this code--you should have a problem with that 
code too. Furthermore, as I have suggested in the forum (and posted a 
patch for), the first thing I would do with this if it were up to me is 
move ccache and distcc out of makepkg and ship them as builenv_ext 
scripts. Then you'd be shipping something that makes this unsafe code 
work just the way the same unsafe code works in tidy.sh.

 >quoting

Sure, no problem. That also needs to be fixed in tidy.sh.