mozilla-devscripts should place extension configuration files in /etc automatically

[dkg]

http://bugs.debian.org/558490 suggests that xul extensions should automatically place their default preference files in /etc, so that they will be treated as conffiles and maintained across system upgrades, allowing local administrators better configuration control.

Attached is a patch to install-xpi to do this automatically, as described in the debian bug.

[Benjamin Drung (bdrung)]

<asac> we dont want all .js files to go there
<asac> what we should do is to guess a name that is alphabetically lower than all other preferences fils
<asac> create that and link it to an empty file in /etc/
<asac> in that way admins can change the defaults
<asac> without loosing ability to reset to package defaults
<asac> like the file we have for ubufox
<asac> bdrung: we have 000system.js there
<asac> thats a link to /etc/...

asac and I discussed the best place for the location in /etc. The result was to use /etc/xul-ext/PACKAGE.js. PACKAGE should be the package name with stripped xul-ext-.

Example xul-ext-adblock-plus:
* create a file empty file /etc/xul-ext/adblock-plus.js
* create a link in /usr/share/xul-ext-adblock-plus/defaults/preferences/000system.js pointing to /etc/xul-ext/adblock-plus.js

The option to disable this behavior should start with --disable-.

Your patch contains some conversions from tabs to spaces (in the usage function), but I can't find any tabs in our branch.

[dkg (dkg0)]

I have no objection to the suggestion that /etc/xul-ext/ is a better location than /etc/mozilla-extensions, given our package naming scheme. i do have other concerns with the above proposal, though.

asac's comment suggests that xul apps will load the extension preferences in alphabetical order, first-match-wins. I don't know the specified behavior well enough to know that to be a guarantee (though i'd be satisfied with a link to the right spot in the xul extension docs).

I'm also not convinced that we want an empty file as the configfile -- that seems pretty unhelpful to the sysadmin. Most sysadmins use the system-supplied default config files as shipped with packages, and tweak them as needed. I don't know if i've ever seen a package ship with an empty config file.

If the concern is about a reversion to the packages' default preferences file, we could place another copy of it in /usr/share/doc/xul-ext-foo/. Then reversion is as simple as:

 cp /usr/share/doc/xul-ext-foo/foo.js /etc/xul-ext/foo.js

(sorry about the errant spaces. i tried to fix all of those to conform with the style of the file, but i guess i missed some. i'm not attached to them in any way)