proposal for ghc-pkg to use a directory of .conf files

[Duncan Coutts]

Hi,

It has been common in recent years since the widespread use of package
management systems to break up configuration / settings files that are
used by several packages into a directory of individual files rather
than modifying a global file.

The advantage of doing this is that it makes things easier for the
package managers. Each individual file can belong to the appropriate
package and so instead of having to execute registration/unregistration
actions on install/uninstall it's just another file to add/remove. The
other advantage is that there is no longer a global file that needs to
be modified which means uninstallation is cleaner (most package managers
do not remove files that were modified after installation).

So the idea is that in addition to a single

$HC-LIB/package.conf

file you have a directory of package files

$HC-LIB/package.conf.d/*.conf

Obviously, the package chasing code needs to be tweaked slightly to
slurp in a whole directory of .conf files and $HC-pkg would want to be
able to use a directory as an installed package source.

I had a peak at the code in ghc for dealing with .conf files. I'd guess
it'd be best ok just check if the specified package file is a directory
or an ordinary file and act accordingly. Ie you could say "-package-conf
packages/" and ghc could by default read from $HC-LIB/package.conf and
$HC-LIB/package.conf.d/ or something.

I can knock up a proof of concept patch if anyone thinks this is a good
idea. It should be totally backward compatible, it's ok to use both, but
ditro packagers might like to enforce a policy of using a directory of
package files for external libraries.

Duncan